There are some lesser known poly pistols that are SA. The assumption that Glock popularized the striker fired pistol disregards a lot of history going back to the early 20th century and even JMB. The H&K P7 was well established before the Glock ever existed. The only common poly pistols that are truly singe-action are the XD/XDm pistols where pulling the trigger causes the sear to lower and release a fully cocked striker. Not even the slightest rearward movement of the striker, it's simply released from the sear dropping. The grip safety is added for that reason.
IMO, the best system yet developed is the Ruger SR9/40/45 where after breaking it in with around 300 rounds you'll get the best stock trigger of any poly striker-fired pistol. Like the "safe-action" design, the striker is pre-cocked and its final rearward travel is accomplished by the trigger mechanism. The main difference being that the Ruger's trigger pull is shorter than the Glock's and after break-in it will be light enough to fully appreciate why Ruger added the ambi-safety. For those who were schooled in the 1911 system and want a poly pistol, the Ruger is a natural. Holstering with the safety engaged eliminates any possibility that the slide will move out-of-battery as well.