Why do the palestinians lack SAMs and such?

Why blow yourself up when you could shoot down a chopper with a stinger?When so many smaller terrorist groups have access to almost every military weapon,howcome the palestinians don’t?They’ll get plenty of oppurtunities to shoot down Israeli helicopters because they’re always overhead.Stingers,SA-7s and all sorts of MANPADS can be bought off the market in nations like pakistan so what’s stopping them from buying and smuggling them into palestine?Similarly,they could also buy anti tank weapons and such.