There's similar cross platform integration built into many of the best third party apps. Pick up another device and pick up where you left off. Google Hangouts, Google Maps, CloudMagic and Opera Coast do this with far fewer bugs than the Apple equivalents, while having more features and generally being much smoother and faster and more stable overall. I also like being able to jump between iOS, Android, Windows and OS X while hardly noticing any difference except there's different ways of closing windows and terminating programs.
I'm all for people using what they like and what works for them. I'm glad you have a configuration that you like.
The reason most people
don't do what you do, however, are multiple.
Google Hangouts: requires a google+ account on both ends for maximum functionality. Requires using their crappy interface on OS X machines. No thank you.
Google Maps: a decent alternative to the built in maps app. I do like having street view as an option. I still find myself using the built in maps app more frequently, though. The vector nature of the maps means when I lose signal (I live in the mountains, very rural), my maps app still has a very large range I can drive through and still have maps available. I also like that I can bring up a location/route/etc using the OS X Maps app and have that synced to my iDevices natively. Out of all the alternatives mentioned, this is the one that provides the most comparable experience.
Opera Coast: no tabs -- uses 'tiles' to keep track of favorite websites instead, or a separate tab-like interface on recently visited sites. Recently-visited only synced to other iDevices, but not actual computers (eg. macbook pro, etc). Number of favorite tiles limited to a 3x4 grid, recently-visited limited to 7 (really? yes): newer visited sites pop off older sites. For my usage patterns, recently-visited (instead of tabs) websites is useless. I keep lots of tabs open for sites I go back to frequently (right now on my phone I have 15 open tabs, and instant access to several dozen more from my macbook pro, mac pro, and iPad). I don't want those pushed off the end of some queue just because I visit a lot of other sites in the interim. Bookmarks are not a satisfactory replacement for tabs, either. With Safari, my open tabs are synced across all my Apple devices, iDevices and OS X devices. Opera Coast is an interesting attempt at a browser, but far too limited in important areas.
CloudMagic: I'm having a hard time finding something this does, that I want, that I can't already do in a similar fashion with the built in Mail app. I already manage half a dozen email accounts from a variety of different services, can do searches across all my inboxes, etc. As well, the upcoming Mail Drop feature of iOS (and OS X) mail is another extremely compelling feature to the built int Mail system.
In a nutshell, that's why most people use the built in apps. They provide the majority of the functionality the majority of people need and provide a great native cross platform (iPhone/iPad/OS X) integration. In order to even come close to that using third party apps, you have to install a slew of extra apps, in some cases create extra accounts with different providers, use different interfaces on different devices, and still get a substandard set of functionality in many cases. The pain level involved is just not worth the lateral (or even down) shift in experience.
