| Do they not make old style Christmas lights where there are sockets
| to screw in bulbs?
Sure. Both classic sizes (C7 & C9) are readily available. They also
have miniature bulbs with covers to make them look like C7, so you have
to be a little careful.
| It sounds like the issue isn't that the bulbs are in series, that's merely
| a slow process to find the dead bulb, but that they are no longer socketed.
All the miniature lamps I've seen are still socketed; however, the sockets
and the connection wires to the bulbs are not exactly robust. Even if you
use a binary search as proposed by another poster to minimize the number of
bulbs that you have to remove and re-install, it isn't entirely unlikely that
you will break or at least deform the contacts on a good bulb in the process
of searching for a bad one. That gives you a moving (and growing) target...
| That would make them far more throwaway than the old style Christmas
| lights. On the other hand, from the flyers I see one can get them pretty
| cheap, so maybe nowadays people toss out the Christmas tree with the lights
| still on it.
They are pretty cheap to begin with, and it is fairly easy to hit the 75% off
sale point after Christmas so you can stock up for the next year. A couple of
years ago I found a 90% off sale, though there wasn't a huge variety left. At
those prices there just isn't a huge incentive to repair dead strings, though
I don't discard good ones.