There is a big element of "not my problem" and avoiding liability. The vast majority of electrical installations are not regularly used by foreigners. Doing a standard electrical installation, even in places where foreigners may regularly be present is the easy and legally safe option, if those foriengers chose to use hazardous low-quality travel adapters and give themselves electric shocks that is not the installers problem.
also as harper says, the multi-standard sockets you show in the picture are highly dubious from a safety point of view, and unlikely to properly meet the standards for any of the plugs they accept.
That said, if you are in the UK and want to provide sockets for visitors from Europe, I would say the following.
UK law, for owner-occupied properties (for rentals the situation is more complicated) only requires that reasonable provision is made to ensure electrical installations are safe, it doesn't actually require compliance with any particular standard. That said, BS7671 should at least be regarded as heavy-handed guidance. BS7671 forbids, in most circumstances unpolarised sockets, so German sockets are out, but French sockets may be considered acceptable.
Also the UK normally installs sockets on 32A ring circuits, this is substantially higher than the breaker ratings used for socket circuits in most countries. To keep this safe, we have fuses in our plugs, but obviously a foriegn plug won't have that.
Also if you do anything unusual in your home, you want to be able to reverse it, and put it back to standard if/when you decide to sell. That means you want to avoid unusual wiring or weird-sized foreign mounting boxes.
Fortunately there exist, what are known in the UK as "Euro modules", I have never found a formal standard for these but several manufacturers make modules and plates and they are in-practice interchangable. On a standard UK double backbox you can fit a four module plate.
A french socket module is 2 modules wide, so on a double plate, you can fit a french socket, a switch and a fuse. When you come to leave the house you can easilly remove this and replace it with a standard double socket.