Thinking back over the years I realise I've only ever bought one bike fully assembled from a bike shop - and I can't really remember, though I think I gave it a somewhat brief inspection in the shop. All the others I've built myself, have been second hand, or bought online - and I do check them over very thoroughly when they come out of the box! I would ALWAYS check the frame, the set up, tightness of bolts, brakes, gears operation, grease on seatpost, QRs, pedal threads etc. etc. NEVER just jump on and ride.