Maybe I can share an example of how I might have "locked" myself into the Apple ecosystem.
I own a variety of Apple products. Currently using a 6S+, iPad Mini 2 (soon to upgrade to the next iPad Air 3 or whatever it's called), 2011 11" MBA, 27" iMac, Apple TV 3rd gen and 4th gen.
I have my 3rd gen Apple TV installed in my classroom (I am an elementary school teacher), which I use to airplay my Apple devices to the interactive whiteboard. Because airplay only works with Apple products, that's a very strong disincentive to switch to any other competing product. I am aware there are other devices out there which do the same thing for other brands (like the EZ-cast dongle), but my set up is working seamlessly and reliably for me and I see no need to change yet.
I like being able to do stuff like use airdrop to pass files around my Apple products, or take calls on my iPad via Continuity, or transfer a task to another device via Handoff. Again, bringing a non-Apple product into the mix would mess up the harmony I am enjoying. My photos are synced via icloud photo library, as is most of my data.
There are benefits, like paying once for an app and being able to install it on both my iPhone and iPad, or iMac and Macbook. Moving away would mean having to purchase those apps all over again on the new platform (and I do spend a lot on apps), not to mention that some apps like Overcast, Tweetbot and Fantastical remain iOS-exclusive.
I am subscribed to Apple Music over Spotify because the former has Siri integration and is also available on Apple TV. I use Apple Maps over Google Maps as the former is "good enough", and my personal stance is that so long as Apple's offering meets my needs, I will use it over the competition. I have recently moved back to Notes from Evernote. And I do see myself eventually getting an Apple Watch down the road once it gets "good enough".
Basically, what Apple has done here is offer me an integrated solution that "just works" for most part, so long as I stay within their ecosystem. I understand that the deeper I embrace the Apple ecosystem by using their services over more platform-agnostic alternatives such as Google's, the harder it will be for me to leave in the future should I so desire and maybe that's precisely what I want deep down inside - to continue to use Apple products for a good many years to come and have a compelling reason not to switch.
But basically, my Apple products and services work well and play well with one another and that's all that really matters to me.