Which is stupid anyway, rent shouldn't depend on the number of people in the unit, you are paying for the apartment/house/etc, not some goddam per person usage.
Pets tend to destroy a lot of stuff, intentionally or not. If you are renting out an apartment and would have to replace the sofa because a tennant's cat doesn't have a scratching post, versus renting out to someone who doesn't have a cat and that problem vanishes. Pee on the floorboards can get into them and bloat (i.e. pet misses the litterbox, just wants attention or got sick). You can't control these accidents, unless you put them in diapers, which nobody obviously does.
The deposit only covers so much; for example if the deposit is $1000 in damages, but what if the animals end up causing $2000? Then you only pay $1000 when the overall damage is assessed.
There's almost no tenants rights laws in most of America. Gouging for every last little necessity is very standard. In fact, most places will try to charge you to apply to rent the place, and will try to refuse to show you the full lease terms until you pay for that. I've chosen not to rent many places just because they didn't want to show me the full terms before I gave them $25 for an application fee.
$25 may not be that much, as they always say, but usually I'm looking at 20+ apartments. That shit adds up fast.