Senior Shopping Scenarios

I’ve nothing but respect for our Senior Citizens but I’m wondering why they choose to shop over lunch time when weekday workers are trying to fit in jobs during lunch breaks.  Today, I queued at the Post Office for 40 minutes as I had a parcel to weigh.  For a considerable period, the queue was outside.  In order to stave off boredom and distract myself from the cold chill in my feet, I conducted an unscientific poll.  Of 24 would be customers, 19 of them were elderly people who could shop at other, less busy, times.  My question is Why?