Why do People have empty Parties?

Hello friendshaped People :) I am not sure, if this is the right Forum to post in, but it seemed to be the best fitting. My question as stated above: why do people have empty parties? I acknowledged this more often over the past few weeks as more and more people seem to do that. For me, this is super annoying, as they appear in my clickback-clicklist over and over and over again and I have to go out of my way into their fields and click there, to "get rid of them" from showing up in my clicklist. This is especially annoying when they dont even have Pokemon in their first field. Id understand, if it was used to lure people to the first field and maybe get a full field of clicks instead of just 6 in the Party, but usually its only a hand full of pokemon that are to be gifted away for free or whatever. Im trying to understand this new "trend". Thanks in Advance and have a wonderful Weekend. :)

i dont know either lol XD

They're probably either out of adoptions for the day or are going to be offline for a while want want to "save" some of the clicks for when they're back. I sometimes do it when I'm just not playing much that day and don't want clicks at all. The "clickback" link at the top of the page should filter out empty parties by default, but it only opens up to 10 at a time instead of up to 50. The users online list also has a filter to hide users with empty parties.