We converted a double garage into a massive playroom but retained the back 6ft deep space across the entire back of the garage for storage. We have floor to ceiling shelving throughout so it houses everything, except garden toys which are stored in a storage box outside and a shed that houses the push bikes.
An extra room banked with storage for all the toys, board games, craft stuff, all coats, shoes, wellies, bags, sewing machine, ironing board etc etc is worth so much more to us than a place to park a car. Our drive will hold 4 cars anyway so we didn't lose any parking.
The playroom (had it for a decade) has allowed for people to stay over, toys to be left out such as train track, scaletrix, marble runs, a place to have a dance to a disco ball, an easy to clean space for painting and playdoh, and now a space for gaming computers and desks for homework.
I think the number of people who park their cars in garages is very few compared to those who have converted them. After all my car does not need its own room. As for de-icing the car, out of 365 days how many do I actually scrape ice on? Compare that to the daily use of the playroom.