The thing about Path of Exile and other action role-playing games is that despite the former's departure from a lot of the conventions in the genre, it still stays faithful to the basic formula, thus why they have a lot of commonalities. For instance, farming is a crucial part of playing an action role-playing game, wherein you gather experience and items in order to get stronger. There is also another thing they have in common within farming, and it's mostly exhibited by the players themselves.
Whenever a common or undervalued item gets dropped, they're just ignored. Picking them up may be a waste of time and inventory space, and it's even more time wasted when you pick one up and have it drop it to free up more inventory space. This is something that you'll see all the time in action role-playing games, and a few of the more recently released ones have clued in to this and taken measures to make sure that there are a lot less item drops to be ignored by decreasing item drop rates and making sure that better items are dropped so that there's more chances of them getting picked up.
In the case of Path of Exile items, with its unique economic system, a lot of those POE items are currency items that are pretty much money. Of course, most people would be picking them up since they're of some value and can then be combined with other currency items to make more valuable ones. However, there may be some players out there who have gotten so rich that they don't even bother anymore.
Perhaps that's a waste, especially since currency items don't take up that much space in the inventory anyway. Then again, in other action role-playing games, you'll see players who don't even pick up smaller amounts of gold that get dropped. In newer games, auto gold pickup has been implemented, so they don't even have to think about it anymore. Perhaps by saving a click and just moving on each time, you save up more and more time that you can use for fighting bosses and doing other more "important" things in the game.
Do remember that with each item dropped, a decision is made to whether pick it up or not. That adds to much of the decision-making that goes on in the game, including that in combat and elsewhere. You can make it easier for yourself by not having to pick up anything at all unless it's a rare or unique item, but that still amounts to a micro decision for each item drop as you play. It's not to say that this process should be any bit stressful, but it does go to show just how things work in most action role-playing games.
It's not really a problem or an issue that needs any addressing. It's just an interesting bit of behavior that you see from players in the game, and it's worth noting why it happens and what goes into that way of thinking. By paying more attention to such small details, you may then form your own hypotheses in your head and test them in the game, letting you become just a little bit better as a player.