Plastic, Cheap , legal, long lasting. Some claim health issues, cancer yada yada who knows. PVC is what I've installed mostly on homes but PEX is common here today. CPVC may be an option I've never used it for water service but hear that sometimes sch 80 (thick) is used on hotels etc.
Copper is still an option and its higher cost may or may not be significant IE 30 foot service not a big savings running plastic.
Other types of "poly" might be used still I have no knowledge on them
FWIW PVC was overwhelmingly the most common during my career in So Ca but it could have changed since my house plumbing career has evolved in last 15 years to other aspects of the piping trades
