No one is forced to buy Airpods, but the first class integration that the product gets which others can't gives it a competitive advantage. This is besides the power to push the product through different channels to customers of iPhones, iPads etc.

Another example is, no one is forced to buy Apple Music, but for sure it pops up front and center when you buy a iOS device or Mac. In fact, even when I keep removing the application from the Mac, on a version update it comes back again. It has integrations into the system and other core system apps that other products can't get and defaults matter. On top of this they will give you free subscription for 3/6 months when you buy a new device knowing full well that most customers won't bother cancelling. All of this behavior takes the air out of competitors like Spotify and is extremely anti competitive.

I don't even want to get started on iCloud etc.