Aside from what the law actually allows for (and states) see comments by Alceste and G S, it's a matter of public perception as well. 

Some women--especially older women--are incredulous that unexpected kissing and bum-patting are defined as sexual assault. Some women simply have accepted this behaviour all their lives. In their earlier years--and now--some may have been flattered by it to some degree (depending on the man,) or shrugged it off as an irritant but basically harmless. It would appear there is a big difference between "unexpected" and "unwelcome."

These were my surprising conclusions after hearing a number of post-60 age women discuss the issue recently. I had expected them to raise their right fists in a show of unanimity and support for younger sisters. By no means unanimous. Among the attitudes expressed: "What's the problem, here? What's WRONG with these young women?"