It makes sense that you’d need a special tool or kit to replace a cracked screen, but why should I have to send away my laptop in order to upgrade the hard drive? Why should I have to be without my phone or tablet for a week while the battery is replaced because it will no longer hold a charge?
A computer becomes more useful the smaller and faster it is. No one, other than geeks, ever cared how computers were put together, or how they worked. They only cared how they could use them to design a building, or research brain injuries, or plan a trip to Africa to drill a well. Real work.
The argument for repairable hardware is similar to the argument for open source; it misses the point of computers.