Depends on the location, but around here solar for heating is completely useless.

In Germany (which is farther south than the nordics and gets far more sunlight), solar panels are already insufficient for heating half of the year. On a typical single-family home, you will get at most 10kW peak power solar on the roof, which you can reach in the summer months when there are no clouds. In winter, those 10kWp will generate at most 5kWh of energy per day. Which is a factor of 4 to 5 below the 20 to 30kWh per average day for heating (with generous insulation). The farther north you go, the worse this gets. Half of the nordics get essentially no sun at all in winter, and are quite a bit colder than Germany.

So you need something other than the sun to heat your home in winter. A heat pump can double, maybe triple the solar energy you might get on sunny winter days, but that doesn't usually cut it. So you need grid electricity, wood or fossil fuels. And when electricity prices are as low as in the nordics (around or below 20ct/kWh), heat pumps are totally viable.

Adding solar can be sensible for cooling in the summer months, and maybe a bit of hot water, and heating in late spring, early autumn. But for winter? Totally useless.

And while you could do long-term storage, that will cost you several arms and legs, tons of space and a huge maintenance hassle. And if anything should go wrong with your storage, you have no heat all winter and better have an emergency plan...

In Norway heating is needed during winter, and there is 0-6 hours of daylight depending on how far north you go.

Going north from wherever in the world you think about, there exists a point where heat pumps become profitable.

(Eventually you drop the solar panel and only go heat pump though.)

tripling the heating/cooling power isn't "needless complexity".

Full solar heating pretty much works if either you have some truly massive roof area or live in place with no winters. Here solar power is at most 1/4 of summer one, at time where you need it most.

Remember, even with free panels, roof space is limited.

Steam and hot water pipes are extremely expensive to install, far worse than electricity, fibre, water or sewage.

You need to be more leak-proof than cold water pipes, because loss of pressure with steam and hot water is much more of a problem than with cold water and cannot easily be solved by just adding more cheap water. Pipe materials have to be more resistant to corrosion because higher temperatures and pressures make them corrode so much faster than with cold water. Closed hot water/steam circuits also mean that there won't be a protective limescale coating on the inside. You need insulation that you can bury and which will last for at least 40 years, which is even more expensive than the pipes. And the insulation will double the pipe diameter. And the insulated pipes have a larger keepout area that needs to be kept free of rocks, other pipes and mechanical strain because the insulation is soft and sensitive to those things. Since usually the pipes aren't operated in summer, and since generally thermal variance is far higher than with cold water, thermal expansion needs to be taken into account, so you need expansion corners, sliding sections, different valve constructions that are tight in all temperatures, etc.

And even with perfect insulation, you will loose approximately 30 to 40% of heat in your piping. So all of this is only viable if you don't care about the cost of the heat, your consumers can (be forced to or persuaded to) accept at least 30% higher prices per kWh compared to their local boiler, not to mention the capital cost.

There are only some areas in Europe even, where those kinds of installations take place: Densely packed inner cities with largely rented-out flats in appartment buildings. There, the landlords/owners avoid the cost and risk of a local boiler and don't care about the running cost of heat, because they don't pay for it. In smaller towns, like in the example, mostly public buildings like schools use those kinds of district heating systems, because the municipality doesn't care as much about cost of the heat, and more about cost of maintenance of a hundred local boilers vs. one centralized system. And in the end, it's taxpayers' money, so they don't actually care that much, headlines and opening ceremonies are more important than that.

Individual home owners usually do have their local systems, which can be run cheaper than what district heating will charge you. And since city density is lower and home ownership is more widespread in the US, district heating is even less competitive there.

hot water also have pretty high losses, because you need to keep it cycling constantly to keep the heat up (you don't want a case where opening a tap in the morning means letting up the hot water from the 30m length of pipe from the street to your house).

So paradoxically, if your heat is not "free" (cogenerated with electricity) it might be far more efficient to have a boiler in each house (and definitely a heat pump), than to push the heat that far away.

There are district heating and cooling in cities where it makes sense, both Minneapolis and St Paul, plus the University of Minnesota all have district heating and district cooling systems. The Minneapolis and U of M systems are operated by Cordia Energy and the St Paul system is operated by Evergreen Energy.

This is the coldest large metro area in the lower 48 states, so it’s economical to do district heating and cooling here.

It sounds like communism / socialism / marxism to people that are unable to define what those things are.