In business, the landlord is renting a space, and the company renting fits it out. You could spend more than several years' rent on a fit-out, why should the landlord goes halvsies in that case?
Though, yeah, depending on the area I don't expect adherence (or enforcement) to be much effective, which doesn't seem to be the case for where this restaurant was located though
It also works in reverse though - when you leave a premises, you don't have to strip out your custom fit-out and put the space back into how it looked before you left. The landlord can't say "I never liked your choice of lighting, so put it back the way it was", for example.