I have used a crate - for the first time in years of dog ownership - for Bob since he first came to me at 6 weeks, and it is still in use and he is nearly six years old.
He really loves his 'den' and goes in and out all the time, I think he would be lost if I took it away! I do lock it sometimes; mostly when I have a caller, deliverys etc, so he doesn't slip through the door, also when Ebby the cat is downstairs and I can't watch them. And even then he goes in of his own violition, when there is a knock on the door he runs straight in there, barking all the time though to let them know he's about!

Crate are great things but only when used correctly. If need be, when leaving a dog home alone, so that he is comfortable and nothing can be soiled or destroyed, helping with housetraining, and confining at times when he may be underfoot and over excited.
It seems to me, from what you write, that your MIL and niece are using the crates in a totally wrong way, indeed, even a cruel way.

Chris