For me it was definitely the sizes of kits. When I first started purchasing kits (or using Free kits), they were mostly full sized kits. At a later date there was an added option to buy full size or tagger sized kits, at that time I thought the full sized would be better. However, the more kits I collected (free or purchased), it very quickly started to fill up my disk drive. Looking back I wish I knew why they had the two sizes. I did not know back then that it depends on whether you want to print for a physical scrap books or just to make tags with the kit. For me I should have gone with the tagger sized as I used them for tags.
Even now I see Designers with kits that have some very large files as well as some smaller files in them, when they are sold as tagger size kits. Some designers are not resizing files. It’s not only the space on your own drives, but when they are added to a store it can also eat up the hosting space, which makes it more expensive for hosting costs requiring a lot more space online. Now I design my own kits which are tagger sized, and I reduce all my files to make the kits a manageable size.