It used to be pretty standard before the pandemic. Covid has given MAs who maybe offered it before an excuse to stop now, or to charge extra for it. I call it an excuse because I really dont think anyone is " safe" from covid during a session when masks are off, ppl are breathing heaving and distancing is a couple of inches. If one of the people in that room during the session has it, kissing isn't putting someone more at risk and not kissing isn't protecting anyone.
For what it is worth, many do still offer it, but now it is part of that awkward conversation that happens pre-session to find out what the limits are. Eva from CMJ (retired?), Hope from Brass, and Nadia Lovechanko (indy) were the best MA kissers imo though I am not sure that Nadia still offers MA sessions. Recent MA kissing experiences worth pursuing would be Grace (CMJ), Champagne (ALO or Alpha not sure), and Kori (Indy).