I don't and you're very fortunate if you haven't had that experience! They get worse too after you have children.
Mine was batshit, useless as a MIL and as a grandmother. Should have steered clear of the entire goddamn family if I'd had any sense! TG she was well over an hour away and didn't drive, so I didn't have to see her that much but omg, she would phone and say, "haaallo" in a tone that implied her entire family had just died and then regale me with all of her latest ailments and who locally had died, that I didn't know. Thankfully we got caller display and I stopped answering! She used to ring at sparrow's fart every Christmas Day too - our kids never got up early! She really didn't know them at all and she bought the most inappropriate presents.
She minded them once in 15 years when DH took them to his hometown to go to a funeral. They were seldom in her house though that is on DH. She and DH's dad (they separated later) didn't give us a wedding present.
She made it very clear that SIL was her favourite, and then in turn SIL's DS. He was born months after our DS and she commented that "at least SIL had let us have a boy first" - WTAF did that even mean!? She cleaned SIL's house, she minded her DS, she had him for regular sleepovers and when SIL and her partner went away. She talked about him incessantly. Said how hard it was for SIL working with a child. We had three!!
When she did come to our house, she sat on her arse and got waited on hand on foot, by me of course. SIL lived away for a year, and she took a long-haul flight to spend 3 months with them. I got a teatowel, and a bottle of wine from Tesco.
I lost my own mum when my eldest was only 9, but she didn't step up in any shape or form. Mind you neither did my maternal aunt which still rankles. My mother was exceptionally generous to my aunt's gc, but my mum died a month before Christmas, and that was the year my aunt stopped giving my kids and my sister's kids the tenner each that she had been in the habit of giving them.
She rocked up with SIL when my youngest was born with the most cheap and ugly clothes you can imagine, and they absolutely stank of cigarette smoke. I had to change my newborn as they stank too after she held them.
So don't talk to me about MILs!!!! That's only a fraction of it!