Honestly, its because there is no way they can actually enforce it, unless you are parking in their space, its not clear to me how they would even know. ( for an apartment )
In any case, it probably is a good idea to just have a chat about it in the beginning. I doubt its a deal breaker for them.
Frankly, before I bought my place, I tended to fill in just my income line and minimal other information and always got the place. Thats all they care about really.
the one thing landlords needs to be when they start a fight with their tenant, is to be squeaky clean (do you know any landlord that is?).
Long story short, I am not sure its illegal, but I doubt any indivdual landlords have the muscle to actually enforce that kind of thing.
(I am talking about separate units tho. I would never consider a room in a house, in the context of a room in a house, the restriction seems much more reasonable - after all you wouldn't want a bunch of strangers in your house all the time, theft by itself is probably a big enough issue.)
GOTCHA sorta maybe.
In a different thread I asked if someone could waive their rights and you basically said yes sooooo if the landlord had a decent place at a very decent price and someone wanted it badly enough they could let the landlord do whatever he wanted. (Not criminal)
A client of mine, a decent sized commercial residential apartment, rented a unit out to a person who is subletting rooms to two other people. The owner figures it will take six months to a year to kick the tenent out but will do it. Breach of contract. NO subletting.
It's the thin edge of the wedge for him. One or two more people in the building doesn't seem like much but if all 200 suites did the same it would be a disaster.
I've heard of some nationalities who are not as space phobic as the western world sharing beds with workers on different shifts. Picture a 3 bedroom apartment with 2-3 bunk bed per room.
Trivial Tidbit: On a tour of historic Montomery's Inn the guide pointed out that in those days a traveller didn't rent a room or a bed but rather a space in a bed.
Back to the OP the landlord may have been burned by a system abuser and may think if he gives an inch you take a mile. How you convince him depends on how fixed he is on the rules. Unfortunately there are very educated system abusers out there that really burn people badly.
I personally knew one that seemed to be the nicest person in the world, well educated professional, charming, not bad looking but I know she and her SO took one home owner for over $18K in unpaid rent. Lies after lies.