Purely speculating...

Modular phones will create opportunities for high quality audio drivers for Android.

Apple products are synonymous with quality audio, and Apple's success is partly attributed to it's investment in music technology.

A brand like Beats which is popular with young audiophiles could potentially transform Android into a recognizable music platform if they provided a Beats audio driver and quality headphones.

This is a risky proposition for Apple as it would drive more of their high-end audience to view Android as a serious audio contender.