Uhm.....back when? In the UK out of the 9 houses I rented so far 8 were 80+ years old, and the last one was "only" 40 years old. Installation of solar panels on houses this old also presents some challenges, as most of them will have original roofs quickly approaching a full century. And if you need to replace the roof just to install some solar panels it quickly becomes an unprofitable idea.

Who cares? Statistically most houses in most places don't have solar. No amount of justification or argument will go back in time and retroactively change that historical fact.

There are other investment options for something that has no liquidity and doesn't result in a profit for 8 years or more.