My dad has one – useful every now and again – but not for me now we have a van that won’t go through the door 🙁
They bought the house new and got the builder to leave an unfinished bit to the garage floor that dad then dug and concrete lined.
It always used to gather a few inches of water, but turned out it was wind blown rain tracking under the garage door. A bitumen coated strip of wood stuck to the floor behind the door blocked that and it now stays dry.
There are ready made plastic / grp mouldings that you can line them with – maybe easier than all the prep, shuttering, concrete etc?