1. Goals are ever-changing.
Perhaps you make a list at this point in your life filled with goals and this you want to accomplish before you die. Going off of the assumptions that bucket lists are intended to be accomplished at a moderate pace (a lifelong pace, if you will), you'll most likely not want to accomplish the same goals for your entire life. Aspirations are fickle and evolve as we do, and bucket lists aren't orientated to facilitate this sort of growth.
2. Placing satisfaction on external factors is dicey.
It's safe to say that many people make bucket lists out of dissatisfaction with their current lives in hopes that things will improve if they take action, in the form of crossing off tasks. But what does this say about happiness? Will the happiness be lasting if it does not come from changes made to the individual? Probably not. Instead of placing one's value and satisfaction with life on the ability to complete tasks, we should be satisfied within ourselves first. That is where intrinsic happiness comes from, which follows us no matter what we're accomplishing.
3. You'll most likely never complete it.
Another thing about bucket lists is that...they don't get done. And what's the point of making a list that doesn't get done?? Please, someone, tell me. As aforementioned, as one grows and evolves and their goals changes, things will just be added and added to the list. To some the endless mountain of tasks many seem motivational and a propellant to accomplishing more, but to me, it seems counterproductive.
4. If you ever complete it (which you won't), then what?
If you're one of the only people on the face of the Earth to accomplish everything on your bucket list (while still being alive, of course), what do you do next? Logically, you may as well die, right? Since there's nothing else you want to do that would bring satisfaction to your life. Yeah, no, I didn't think so. The premise simply doesn't make sense, and it's not reasonable to expect to be completely happy with your life after you cross a few things of the checklist.
So please, do yourself a favor, and stop making the Bucket Lists, and just go out there and live. You'll be happy you did.