it's mostly because WeChat has gov protected monopoly over China, while Western chat apps operate in fragmented environment so it's really difficult to convince user to switch to them for payment if half of your contacts can't receive your payment and same goes for other functionality and building this features require critical mass of users which is just not possible in open market (well it's not possible on Android since Google seem to be suicidal regarding chat, is perfectly possible with iMessage)
it's mostly because WeChat has gov protected monopoly over China, while Western chat apps operate in fragmented environment so it's really difficult to convince user to switch to them for payment if half of your contacts can't receive your payment and same goes for other functionality and building this features require critical mass of users which is just not possible in open market (well it's not possible on Android since Google seem to be suicidal regarding chat, is perfectly possible with iMessage)