I dare say until about 10, maybe 15 years ago, no one here threw any Bachelor/Bachelorette parties. Same like no one "celebrated" Halloween. US stuff that kind of spilled over here.
They're usually harmless, but actually yeah, there may be a stripper involved *yawn* (saw that at a bachelorette party), then there's usually some pretty boring semi-embarrassing "fun games" in a busy street somewhere nearby, sometimes in costumes, then a bit of drinking, eating, whatnot. That's probably it.
As should be obvious, I'm not a fan