If you take a sublet, you want to be sure that you are dealing with the prime tenant, and not an imposter or individual who has already sublet the apartment from the person who's name is actually on the lease. That would make you a secondary subletting tenant at best, which is probably illegal without the landlord's permission. With a rent-stabilized lease, it also presents the landlord with an opportunity to evict the prime tenant and all subletting tenants, freeing the apartment from regulation. Rent-stabilized leases have strict rules governing subletting, which must be complied with if the regulated status of the tenancy is to stay intact. There's nothing worse than a nasty surprise when it comes to the roof over your head.