Because every paint manufacturer says to wait (typically somewhere between 60 and 120 days) before waxing a newly sprayed finish.
Sanding, washing, compounding and polishing? People make that up because somebody misinterpreted the waxing thing and it grew from there. Paint manufacturers give you specific instructions on how you're supposed to do those in the first so many hours after spraying.
There is no reason to wax a car in the paint shop. The rest of the stuff is part of the painting process.
Ovens and IR panel heaters only knock the first few hours off of the curing cycle, enough time to get to sand, cut and buff right after spraying instead of waiting until the next day. Full cure still takes weeks.
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