The difference is in the delivery method. Android malware gets distributed by 3rd-party (pirated) app stores and apk downloads, where every victim actually had

The difference is in the delivery method. Android malware gets distributed by 3rd-party (pirated) app stores and apk downloads, where every victim actually had to do something questionable to get infected. There haven't been many reports of malware attacks on Android from doing innocent things like opening emails. WannaCrypt on the other hand relied on NSA's ETERNALBLUE and DOUBLEPULSAR exploits so that computers sharing a network could get infected without doing anything. Aside from that, most people would just reset their phone if they got ransomware since most of the important data on a phone is already backed up to the cloud. So there's less of a payout as well.