I really don't understand the problem here.
If you buy a Mac it's because you want the platform. If you are more concerned about budget, then you buy a PC. If you like tinkering, you buy a PC.
If you survey the general population (not those on a forum), how many people have ever upgraded the hard drive in their laptop (or even desktop), I bet you're looking at a fraction of a percent.
If you're saying upgrade cost is a factor - these aren't regular SATA SSDs. They're PCI-e ones. Chances are, they're based on the 960 Pro line. In the UK, Apple charges £1080 for the 2TB SSD. Want to buy a 2TB PCI-e SSD yourself? £1200.
http://www.novatech.co.uk/products/...nal/ssdsolidstate/pciexpress/mz-v6p2t0bw.html
And if you have £2600 to drop on a laptop, and need a bigger SSD, that's hardly going to be a deal breaker. People buying these machines aren't those living on the breadline. And as for the SD card comment - seriously? Who has used an SD card to upgrade their laptops internal storage in the last decade?
Then there's the longitivtiy of these machines. I have a 2011 iMac, which still works great. I'm currently typing on a 2014 MacBook Pro (15") and I see no reason to upgrade anytime soon - they're far from disposable. My parents, who aren't exactly power-users, have been through 3 Windows-based laptops (2 HPs and a Lenovo) in the last 3 years.
As for adapters, it's early days. Remember when we had to use a thunderbolt to firewire connector to support legacy firewire devices? Or DVI/VGA adapters to connect a VGA monitor to a MacBook Pro? We are already seeing USB-c hard drives and peripherals on the market, and when other manufacturers start using USB-c, and it gains mainstream support, that won't be a problem.
Every time there's a change, people moan. Normally, people who the change never affects (hands up anyone here who has complained and has actually bought an upgraded SSD for their current MacBook Pro?). Yes, it means less flexibility when it comes to repairs, but many of the components which fail are removed, reducing the chance of failure (any ex-geniuses here will have lost count of the number of HDD flex cables we used to replace on MBPs).
MacRumours members will moan. iFixit (who make a living selling spares) will say it's terrible. But yet, people will buy it, and reviewers will say it's great. In 3/4 years we will wonder why we ever needed a different cable in a specific port to charge our laptop.