So what you're saying is that saying Merry Christmas to someone creates the expectation that they will give you gifts, or the expectation that you will buy them gifts, even though 95% of the time, people don't exchange gifts with the person they are saying it to? That just doesn't make sense.
The reason we make gifts is because it is more fun. Plain and simple. It is exciting to see what the person who drew you made. It has nothing at all to do with being anti-consumerist, and everything to do with spending time and effort creating something that another person will hopefully like.
I don't know what strange world you inhabit, or if you spend Christmas time sitting by yourself in a culture neutral dwelling, but the vast majority of adults do the gift-giving and the big meals because they like to please the people they love. They would do this regardless of corporations or consumerism or even advertising, as they have for literally centuries.
That capitalists use this tradition says nothing about the validity of the tradition itself. They use everything, even the most pure and wonderful human emotions, churning up authentic experiences and spewing out shit. Perhaps instead of going crazy and throwing out all the things they've corrupted, we can reclaim them by insisting on authenticity, saying Merry Christmas because it is valuable to you, or Happy Holidays if you prefer, or nothing at all, for that matter.