They had no choice but to keep reusing old hardware after how badly BlackBerry 10 devices sold in the beginning. Creating all of the drivers required for all of the new hardware just to run one phone maker’s OS isn’t cheap. It’s not that BlackBerry wanted to keep using the same outdated crap over and over, they didn’t have a choice.
Thorsten gets a lot of crap around here, but even he was smart enough to know and to actually say, that “for BlackBerry 10 to have a chance it has to have a successful launch and improve from there”. The Z10 and Q10 launches were disasters, yet it only got worse from there with each additional BB10 device sold. By early 2014, it was clear to most that BB10 was already in zombie mode. BlackBerry never made a single penny of profit off of BlackBerry 10.