I have almost this exact issue on my x3. ~25k miles in and front tires are badly worn on outsides only. Rear and inside tread are almost perfect. I noticed the issue during the first half of my cross country trip in may (~18k) and had them check it on the way home. I have a staggered setup and the bmw service tech blamed that instead of the alignment. Upon review it’s very clear that the alignment was the reason for the wear.
It’s quite an annoying issue on a lease, since I’ve only needed to service it every 10k miles (basically twice) and if they didn’t pick it up on the first service (they didn’t) then it’s just like hey man sorry you didn’t check out your tires. Like max said, At this point I’m saving the money for a new front front set, which I was basically guaranteed to pay for given the issue.