Why do I "deserve a treat" when I accomplish something?

Is this a "rule" or something that everyone has been taught. I've never fully understood this, yet people around me seem to think that when anything positive happens, you "deserve a treat".<br><br><br>The "treat" is necessarily related to these positive experiences, either. For instance, say you're successful in some sort of argument; you "deserve a treat" because you won something that you're entitled to, if that makes sense.<br><br><br>This has been a recurring theme in my relationship with my partner, where I'll ask if we can do something frugal, and they'll say "no, let's go for "insert cool expensive thing here"" because we "deserve a treat" after something positive happens.<br><br><br>I've seriously never understood this mentality and would love to hear your thoughts and experiences! I never felt like I deserved a treat after accomplishing something, and I just don't get it.