No matter how few items an old person has and no matter how few full service lanes are available and no matter how many self-check-out lanes are available, the old person will almost always make a beeline to the full service lane.
Are they scared of the new technology? Maybe they just want someone to talk to. Who knows. But when I've got a shopping cart full of groceries and watch the old person insist on using the full service lane for a handful of groceries, it drives me nuts.