Ah - good to know you customize the OS and browsers to replace the TC/IP stack, datagram socket handling, DCOM, virtual memory management, policy support, image handling, flash and script support, interprocess coms, LDAP, AD, etc., etc.,etc.
A common aspect of SecIT involves
limiting user's options to protect them from themselves. It doesn't take much to be aware of the tremendous support costs of keeping systems operable and secure in the hostile environment that irresponsible market development and consumer perceived demands have created.
Eight years ago, a government client asked what she could do to avoid the high IT support cost of keeping her data systems secure. I said simple - prevent removable media access and don't connect to anything! Of course, being a public entity, this was not an absolutely viable option - but it was relatively inexpensive for internet access to have a physically separated network and PCs (and public viewable PCs for most staff at that - to avoid abuse). Their half million in software investment performs as good as the day they were (re)setup eight years ago with <$1,000 in direct support costs due to one failed P/S and a few failed HDs (easily replaced by users - ~3.5 minutes to resetup...) - and no real lost man hours!
Apple chose a similar tradeoff - reduced flexibility and user choice. With an ROI in excess of $50 billion it would be silly to argue that wasn't a good choice for them. Not saying they couldn't have done better - nor that I wouldn't have preferred other choices (like USB support and direct file access upfront, beside the previously mentioned options). But, like millions of consumers, the tradeoffs were accepted.
I've programmed massively parallel super computers down to ASIC SoCs - regardless, the fewer external performance related issues I have to worry about, the better. For the mass market consumer, this can hold true as well.