There are many legitimate reasons to do construction work in the proper sequence.
Carpet or molding first.
If the carpet and baseboards are installed first though the painting process is slowed as the painter takes extra measures to avoid getting paint on the baseboards and the edges of the carpet where it meets the wall.
Base molding or carpet first.
Tile should have a grout line equal to the field of the tile.
Multi purpose reducer is used to transition floors of multi purpose reducer is used to transition floors of unequal height from wood laminate floors to carpet vinyl or tile.
Also keeps caulk and paint problems off of the new carpet everybody makes mistakes has accidents.
Second drywall would wick up moisture from flooded floors or carpet.
I want to get something done and my door case molding and base moulding would be a good weekend project.
The way i like to do it is hang doors first cut jambs lay floor install baseboard and then qtr round.
If you care about doing quality work and not wasting time you paint the walls then install the hard floors cabinetry doors and trim.
Just the other day i was watch a guy putting in some baseboards.
This molding will provide a seamless look when transitioning between flooring surfaces.
First in the event of carpet installation the gap will need to be there for the edges of the carpet to be tucked under.
Should i wait to have the carpet installed or just leave a small gap on the base moulding for the carpet to be tucked into.
I install the flooring first then trim tight to it.
Problem was it made the baseboard look wonky big time.
Base first the carpet guys have their own tricks of the trade.
Coordinates with hardwood floor providing a beautiful finished look.
Carpet layers should be the very last trade on the job.