Hmm, looks like I chose very bad comparison to get a glance of real world difference of TB and usb3. 4big and 5 big are so different products.
I do know that there is use of TB among some video professionals. The thing I've used to criticize is that there is only 0.1% of users who benefit from TB and usually Apple doesn't cater such niche.
If you use software raid, I'd guess that limiting factor is how much you have cpu power for software. If you have hardware raid-5, once again the limiting factor is hardware's processing power.
If you need only 5 or less hdd's in raid-0 you can just use internal hdd's of MP in desktop enviroment. In the field with laptop usb3 is fast enough for 3-disk raid0.
So what's left is need for over 5-disk raid-0 in desktop enviroment or over 4-disk raid-0 with macbook on the field. These are pretty über-niche things.
Eg. if you are a DIT in big productions, you'll use much more expensive equipnment and if you are indie-DIT with no budget, you're better off with cheaper storage than TB-connected raids.
If we really think that Apple wants to offer support for this kind of niche use, then why not anything else? Why not 17" retina? Why not matte retina? Why not to offer wider expandability like modular bays which could be used as ec-slot, cf-reader, secondary or tertiary storage or just for extra battery? Why not giving decent GPU options for hard work? Why they had to get rid of video professionals with shake & fcp?
Much more logical reason for TB to exist in even the cheapest macs is just for PR value. You can say that it has something better than the rest, even if it's probably not even used. Also there's lots of people who like to buy new tech they don't ever need.
You should look at it from another angle. TB allows them to move more out of the desktop / laptop and into external devices (via Thunderbolt displays, third party hubs, etc.) It allows for thinner devices. If they dropped everything but power, audio and Thunderbolt, they'd still have plenty of connectivity options.
I don't see them doing that at this time, as USB 3.0 is supported directly by Ivy Bridge / Haswell, thickness of the connector isn't much more than display port, etc. I could see them going to a mini USB 3.0 connector, but that's neither here nor there.
The LaCie product in comparison doesn't have anything to do with Apple, per se.
Apple has Thunderbolt support, which is pushed by Apple, but it's Intel tech. What is your point?
Do you really think Apple would dump Firewire and marginalize the product by outfitting their laptops with the same connectivity options that all PC brands offer? They added Thunderbolt before USB 3.0, but that was strictly due to the previous generation Intel support for USB 3.0. Apple wasn't going to put a third party chip in there just for USB 3.0.
As far as outfitting their laptops the same as the PC industry as a whole, that's not in their vision, it's not what a vast number of their customers want to see, and it's a strawman that I'm tired of talking about. So I'm done.