I don’t use them, but when I pack a lunch it is usually leftovers, not sandwiches, so it travels in a reusable container with a lid.
I do reuse bags that I have placed other items in, like cookies, crackers and baked goods, and bags used as secondary wrapping for the freezer.
I also use regular ziploc sandwich bags for making hamburgers and portioning out meat for the freezer. Those bags are not reused for sanitary reasons. This is my biggest use of disposable bags, but still not a huge one.