Regarding your particular circumstances, is it because sequencing centers are slow to upgrade to the newest sequencing technology (probably because the investment in the last-generation is so large)?
No. It is because the next-gen sequencers just don't do what the old sequencers (sanger) do (sequence small regions of DNA at high accuracy). The new machines can sequence a whole genome, but if you only want to look at small part of a genome then there is no replacement for Sanger sequencing.
Another surprising reason is the OEM manufacturer of the instrument (hitachi) basically over engineered the machines and built a tank. The machines just keep running and running.
