Vegans tend to see a strong justice case involved when eating animals—there is clearly a specific moral patient being harmed (eaten).
But being eaten is not harmful for an already dead animal, it’s the life and killing before, which your current purchase almost certainly didn’t affect, unless you’re buying live animals or the animals are slaughtered at your request for your purchase. Your purchasing behaviour mostly affects animals not yet born in expectation (although with very low probability does it affect any at all). You could in principle offset your impact on the market before the market could take your individual purchasing behaviour into account separately from things you do which reduce consumption in others. For example, instead abstaining from a specific animal product in one instance, you convince someone else in the same region to do so, if they wouldn’t have otherwise. This kind of offsetting seems much harder and expensive, though, since it needs to be particularly targeted.
But being eaten is not harmful for an already dead animal, it’s the life and killing before, which your current purchase almost certainly didn’t affect, unless you’re buying live animals or the animals are slaughtered at your request for your purchase. Your purchasing behaviour mostly affects animals not yet born in expectation (although with very low probability does it affect any at all). You could in principle offset your impact on the market before the market could take your individual purchasing behaviour into account separately from things you do which reduce consumption in others. For example, instead abstaining from a specific animal product in one instance, you convince someone else in the same region to do so, if they wouldn’t have otherwise. This kind of offsetting seems much harder and expensive, though, since it needs to be particularly targeted.