Both Apple and Kobo are more like boutique bookstores. If you want promotion on either platform you need relationships with the company. Both are happy to meet new authors, and also have reps at all the major author conferences I've been to.

They'll run cool promos and send out mailers on your behalf, if you're in good and have content they want to promote. I've never made a ton on either platform, but I know people who've done fairly well, especially with romance.

The iBooks office was on the Cupertino campus when I went, but the team was tiny and spread out in 3 different buildings. No idea how it's changed in the last few years as I'm in KU.