Only in London, people I know have had both experiences. Letting agencies are really the one pushing. For the landlord, a paying tenant is a good tenant, there is friction in changing tenant: you can lose 1 month rent or need to do some refurbishments. Even missing a few weeks can mean losing any benefit of keeping the same tenant at the same rate for 1 or more years.
Letting agencies offer a service to both the landlord and the tenant. As a tenant you get a certain level of service, like repairs or maintenance. As a landlord, the agency offer vetted tenant, management and various guarantees. They are the one pushing for rate increase as that's what they take their share from.
The real problem with renting is the underlying skyrocketing price of housing. You can't escape it.
Since I've been here the neighborhood has improved to the point that people actually want to live here and not, like when I originally moved in, a semi-OK neighborhood with cheapish rent where you probably won't have any hassles walking to the corner store at 3am.
Then again, I was talking to my landlord a while back and the city was complaining he wasn't charging enough (ie. wasn't paying enough taxes) but he would rather have good long-term tenants than charge "market rates" and deal with all the problems that come with that.
Both sides lost - I had to spend the time and effort to move and they now needed to spend time and money to prep another apartment for rent - but I suppose the pricing algorithm takes this into account and figures that in aggregate the apartment complex still comes out ahead by continuing to squeeze people that don't want to move.
Property markets are perverse in many different ways, most of which don't benefit renters.