The slower ones are probably not paying via QR code, but acquiring points with them QR codes, such as the 50/50 schemes and whatnot, which is a more involved process and can apply to only certain products purchased etc - I usually have a stack of cash, but prefer to pay via QR code paying for gas on most (if not any) gas stations, via my banking app, or restaurants or Makro or Big C supercenters - tho with Big C I'll usually ring up my card, as it seems faster to get the receipt than via phone and scan this scan that.
I also pay my electricity from PEA, and 3BB internet, over generated QR codes at the same time I pay my rent, instead of hauling my ass to nearest 7/11, pay all my dues at same time (well except the water bill that comes handwritten to my mailbox). And now that recapping, I paid my last car service via PromptPay QR code as well, in seconds, instead of hunting the nearest ATM as the bill was a bit larger I envisioned.