Yes, this has the side effect of making them more money and allowing a walled garden to form, but given that the vast majority of users wouldn't do anything different with their phones if a shell was present, this is in my opinion not that large of an effect.
The snide around "clicking on links is dangerous" and locking down the bootloader is unwarranted, because for most people a phone is not a toy (or at least, not just a toy) - it has their communications history, their bank information, their passwords, any many more. And it's really easy to steal people's phones on the subway. This isn't about freedom of computing, this is about the fact that an iPhone in BFU is nearly as secure as a GrapheneOS phone.
There are many problems with Apple software. It's buggy, uses proprietary formats that you can't export, and interoperable with open standards. It's bad, and is the primary reason why I won't buy another iPhone, but Macs have that same problem. On the other hand, being cryptographically locked-down is an optional feature. If you don't like it, buy a computer without that feature. It's harmful to us, to tinkerers and people who want to see how things work, but the average person does not care at all and just wants to be able to open LOVE-LETTER-FOR-YOU.TXT.vbs without having their 401k get drained.