YA know, I often here people say this but in reality......I dont know a single person that has put pex in the floor because they "might" do radiant heat at some point in the future.
Its really not just as simple as "throw some pex in there and cover it with concrete".
It takes planning. Planning out zones.....and paying attention to hot out cold return. And tighter pex spacing around the perimeter. Not to mention 2" thick foam insulation under the slab that you then staple the pex to.
Then, if the garage is much larger than 20x20....moving concrete becomes an issue....because no buggies or wheel barrows. So tack on $500 more to the job for a pumper truck.
I helped a friend do a 40x64 with radiant heat. $3000 in insulation foam board, $1200 in pex, $100 in staples and tape, and $500 for the pump truck.
So for a 33 yard pour....darn near $5000 more just for stuff gonna be burried in concrete for radiant.
So unless people have money to burn....I dont know anyone that actually preps for radiant because of a "maybe". They are either doing it or they arent
signaturedetailers. ITs just too easy to tell others "you should put in pex....." Without actually thinking about the cost