back in the days apple newton was sold at all stores; it was pretty useless and doomed with a heavy pricetag!
i tried android tablets, no update and no external keyboard option, only for one samsung model so you are stuck with that brand; if there was a standard for periferials that would cause more trust, when all tablet producers make their own confusing interface and block updating of course there will be lack of trust.
the ipad is simply very good hardware and very good software (not perfect, alas!) coupled with a functioning ecosystem of apps grown from iphone while keeping the same connector so most thirdparty devices are working, spreading trust in users.
palmpilot was once the main pocket computer on the market and destroyed by everchanging models with different interfaces and stiffened innovation, had they kept to the slow and steady development that apple do, we would all be seeing palms now (their interface is still faster for looking up appointments, adresses and taking notes than the iphone)