They're threatening to evict you, yes. But actually evicting you, in at least some states, can be challenging. I know someone that rented out his entire home (long story), and got paid about three months of rent before they quit paying. It took him nearly two years to get them out. (Last I knew he was suing the agent that vetted them; apparently there was collusion, and the tenant has done this multiple times before.)

The flip side is that if you quit paying your mortgage, it's also going to take months or years to get you out of the house, but then the bank has a piece of real estate. Banks don't want to own real estate; that's not their business. They're not set up to buy and sell real estate. Foreclosing on a house costs a bank a lot of money.