Which reasons? I mean for apartments

landlords don't want to spend money, and it's not like you're going to live somewhere else

telcos lay fibers for free up to basement electrical closets, from closets to each units are on landlords, and to each units to actual wall outlets needs arrangements with tenants. Sometimes ISPs subsidizes that cost, but lots of arrangements still needs to be made.

For one entire rented or owned house, it's just a call and a drill away.