Do you want to carry around the same bag from summer to winter? I guess the answer to that is a big "no."
It is a good idea to change your handbag every so often so that it doesn't become a black hole.
You change your bag every season for the same reason that you change your clothes and shoes. In summer, you frolic around in new summer dresses and a bucket bag or a sling bag. In winter, you'll opt for a warm jacket over woolen leggings and a tote bag. The handbag that you carry around each season has to match with the season.
What's inside your handbag?
Also, the stuff that you carry around in your bag changes with every season. In summer, you would probably take a smaller and lighter bag with just some sunscreen, lip balm, a bottle of water, and some wet wipes. In winter, you'll need a slightly bigger handbag to accommodate an extra scarf, sweater, or gloves in case the cold starts to get to you.
So depending on the season and how much stuff you have to carry around, the size and type of your handbag will change too.
And of course, last but certainly not least, it's about the functionality and keeping up with the latest fashion and trends for that season. The biggest brands from Gucci to Prada to Coco Chanel launch their latest collections during springs, summers, and winters, including the latest and best styles of handbags and accessories.
I look forward to the change of seasons. I get very excited thinking of the new fabrics I will use to create my new line for that new season.