Why is it not recommended to microwave UK or Canadian bacon?
If we are talking about bacon in these terms:



I believe it's because of the meat content difference. American bacon has a much higher fat-to-meat ratio and it's usually thinner, so when you microwave it the thin meat gets crispy (which is, arguably, a good thing in this case).

Canadian and UK bacon have much more meat, and if you microwave it the meat will dry out too much that both texture and flavour will be ruined.