When folks only upload the QSO's they "need" that's a sign they haven't really drunk the LOTW Kool Aid yet. They've just barely sipped it, so they get some personal advantages, but they aren't sharing the advantages with everyone else.
Sure, but at the moment, we are discussing someone with paper logs and possibly thousands of old, mostly dead QSOs, not stuff you did "today".
The benefits for all that older stuff, for everyone, are kind of marginal. In many cases, if not most, the card has been in the shoebox for years (if wanted at all) and most awards (DXCC or anything else) related to those QSOs have long been claimed. And, if you are some W in New York State, not many people need your QSO confirmed to start with. If they did, they got your card years ago.
If someone is "up" for typing in all that stuff (one enterprising Ehamer found an on-line source to pay for the typing!), well, more power to whomever that may be. For the rest, who may be barely or recently computerized, there's no point in discouraging them with the counsel of perfection. They can get potentially interesting results with just the "important" QSOs however they define it (probably rare DXCC mostly) for not much effort.
Going forward, we can hope to persuade them of the benefits of uploading everything. The past? That's really up to them.