Coins with low value need wide adoption before they stop being shit coins... It makes no sense to make micropayments with coin as valuable as Bitcoin, but it doesn't make sense either to use some "cheaper" coin that can't be easily converted to FIAT due to low volume on exchange(s) it is listed on.

There is also a lot of coins listed on exchanges with bad reputation, either because the fees are too high, the customer service is subpar or because the markets are too much manipulated, so getting decent exchange rate is unlikely.

A lot of coins that would be good for micropayments don't have mobile wallets as companies like Google and Apple charge high fees for access to their app stores or developer tools.