If you're renting a place without a lease then it's still considered to be a lease rental as in a month to month lease rental even though you never signed a lease.
You can still be evicted from your apartment or house when renting even without a lease and the landlord can terminate your rental at anytime and force you to move out.
Without a lease a landlord could just lie and tell the cops that you are trespassing and have you arrested for trespassing and be removed from the property.
That happened a friend of mine who was renting a place without a lease and the landlord wanted to sell the house so he terminated the tenancy and called the cops to say she was trespassing on the property.
She was arrested for being on the property and living there without the lease.
Although that happening is rare but sometimes it can.
It's best to always have a lease for renting some place to prove you can be there and it makes it harder for you to be evicted since you have to go through a court process.
Still the landlord can take you to court even without a lease and have you properly evicted.