Apple has 18% of the smartphone market: http://www.idc.com/promo/smartphone-market-share/vendor

And 7% of the PC market:

https://www.google.com/amp/s/amp.businessinsider.com/apple-m...

And greater than 10% in the US.

Even those numbers don't exactly scream users don't care about compatibility.

Apple market cap: ~700B, Microsoft market cap ~500B.

It's almost like they are both successful but for different reasons.

Market cap is a meaningless metric. It tells more about state of mind of general public (greed vs. fear) than about company's well-being

How does having a higher market equal cap users don't care about compatibility?

Market cap is a lottery ticket.

I would assign more meaning to cash hoard:

Microsoft: ~$100 billion. Apple: ~$250 billion.