One word:
Expensive

Harbor Freight has a "High Volume/Low Pressure" spray "kit" that included
the blower. It's not all that different from the "spray" gadgets that used
to come with some vacuum cleaners.

With latex, you have to use the largest nozzle and add the stuff that make
the paint worker with sprayers and, maybe, thin the paint a little to boot.

It's a little faster than brushing but you have to keep cleaning off the
spray tip from dried paint. Clean up isn't too bad.

I find it more useful as a "sprayer" than as a paint set. But it was only
about $70.