All the time with 3/8 and 1/2". The older and more crippled I get it's amazing how many times a day I will use a 2-3ft extension instead of standing on my head in an engine bay or trying to contort into some shape to get to a fastener.
Bellhousing bolts, starters, shocks, motor mounts, torque converter bolts, glow plugs through the wheel wells, CV axles if the inner joint has a bolt on flange (GM and Ford trucks), PS lines, turbo mounting nuts, block mount trans coolers on some Dodge Cummins, brake master cylinders, absolutely have to have one for certain differential carrier bearing preload adjusters, etc.