The issue is many stores use dark patterns and you may not catch on until too late. - Subscriptions impossible to cancel - Silent auto-renewal - Silent price changes - Hidden Fees - Sales of purchase history - Apps released under known brand that are off brand knock offs. - Apps bundled with added cruft (think those download.com installers that installed toolbars and whatnot). - Pirate versions of Teams through off brand store causing licensing audits

A lot of dumber app vendors will just drain the suckers dry and rebrand and if Microsoft pulled their apps from the App Store some unfortunate souls would click the first Google hit and get sucked into the scam.