Stucco should NEVER be painted with house paint. If you're seeing
professionals "paint" stucco, chances are they're "dashing" the
stucco. Dashing is done by mixing a slurry of cement with colorant.
They use a large brush and either "snap" the brush to splash the
slurry onto the stucco, or they brush it on.
Stucco breathes and if you apply house paint, it tends to seal the
pores in the cement (just like you would expect it to work on regular
siding). Once it's painted, it's difficult to go back to dashing.
Either you have to wait years for the paint to oxidize, or you have to
sandblast the house.
This advice comes from years of working in the painting/contracting
biz. We dashed homes all the time. If an owner wanted us to use
housepaint, we would do it, but not give a warranty.