But Apple doesn't have a significant share of the mobile phone industry - Android (Google) does - with I believe Samsung leading the way. So how can it be monopolistic?

The comparisons in other posts is not quite apples - to - apples (no pun intended) because you can't be a monopoly when you're not in a dominant market position.

Lastly, whether or not the examples you mention "benefit" customers today is irrelevant, as you need to consider the possibility that their dominant position would mean that they might not in the future (i.e. customers not acting in their best long-term interest, or companies leveraging their market dominance in the future for non-customer-centric behavior, etc.) Platitudes like "don't be evil" don't persuade me much.

Edit: don't know why folks are down-voting a comment about US anti-trust law.