They probably don't have as much other stuff on the hud. PB2 has:
ammo count, mask icon, 4 different team icons, 4 different team scores, lots of CO2 images, kills, streak, alive counters for each team, all the different items, time remaining, etc., etc. The limit is only 32. The good news is, I've made a customized client-side hud and could implement something that draws a pic depending on which weapon model you have. Won't make it in build 11 since I don't have the time to make the graphics, but eventually it can be done...