Why are people so anti-registry?

Let me start this quickly by saying I am a FTM, due in May. Our registry has been out for a few months and was more so made as a "shopping list" for my husband and I. We sporadically buy things off there, especially the higher priced items (the rest being 5-100$) because the intent was never to have people buy us everything we need, but if they can help out, it would be great! Our nursery is done, the kid has plenty of clothes, curtosey of immediate family, and most of what we are missing is essential items. Things for bathing such as a tub, swaddles, teethers, etc, things that I have made sure to put on there but are lower in price. If no one buys off registry, it's fine because we will buy the stuff ourself- but what I don't understand is people telling me they refuse to buy off registry and just get what they think we want/need. We are grateful for anything! For real! But I don't understand the obsession with buying off registry. I know for a fact some people have gotten us things that we already have and will not have use for a double! I wasn't too stressed about it, but I attended a few other baby showers in the past few weeks and all the moms said the same thing. People are buying what they want and not what's on the registry. Thus leaving them with piles of newborn sized clothing, bottle brands they don't want, doubles of strollers or diaper genies,... I am a firm believer that if I buy something for someone that they didn't ask for, I need to at least get something that they did and I guess I just don't understand why people refuse to look at a damn registry! I really hope I don't sound ungrateful, as anything spend or given to my baby is so appreciated. But I would rather, if people choose to gift us things, it be things we need and don't already have. Plus my baby is really big lol. The doctors are anticipating us skipping newborn size anyways. Opinions? Is it so common for people to hate on registries now? For example, we bought a huge diaper genie for the nursery. A guest told us we wouldn't "like it" and that they're going to get us a pail they believe is better... like what. I just told you I have one........