Purtians - and other fundamentalists - might criticize the connection between Christmas & shopping, but I appreciate that link.
1. Giving Christmas presents demands that you think about the needs of the beneficiary. You have to find out - or to speculate - what she or he might like. You have to invest time & efforts to discover things that might enjoy another person. I believe that you could learn something in this process and that both, donor and presentee, could discover new things.
This reminds me of Christmas during my childhood. Then presents where given on Christmas eve around 6pm when it was already dark outside. In the wake of this event there was a climate of excitement and lustful anticipation. And then came the moment of unwrapping the packs!
2. The Christmas spending spree (and similar events in other culture like Chinese New Year) is certainly good for retailers and a lot of other companies. The tradition of giving Christmas gifts creates tons of jobs and incomes and keeps the whole wheel of the economy running.