I have moderate to severe joint pain in all joints thanks to a pharmacy error that nearly ended my life. On the plus side, every day since has been the best of my life (being suddenly moved that close to one's expiration date can have that effect). The downside is constant pain. I've learned to manage pain quite effectively, but the cost of that effort is fatigue. Managing activity level and regularly assessing my pain level has gone a long ways to mitigating the impact of pain to my quality of life. Carrying heavy items significantly impacts my stamina, so the weight of a bass guitar can be an issue. Balance and good ergonomics can mitigate fatigue. It's a balancing act.
Buying in person, I don't have to think about the weight of a bass guitar. I've spent enough time in my life playing standing up and I can discern whether or not a given instument will be comfortable to play while standing for a while when its already strapped over my shoulder. If its comfortable to play and well balanced a weight of 10 or more pounds may well be just fine. Buying online, though, removes the possibility of assessing comfort and balance. This makes an instruments weight critical information in deciding whether or not to move forward with an online purchase. Having to ask the seller for the weight of a bass guitar in a private message isn't a hassle for me, but I have to know the instruments weight before committing to purchase it online. If the seller cannot provide the guitars weight in response to a request then I have to pass on a purchase.
There are some for whom weight isn't an important factor. This seems like an upside to me as it's one less factor to have to balance against others when making a decision to purchase a guitar online.
Now, as a seller, it's more hassle for me to field the same question over and over in response to private messages than it is to just list this information. When I post a guitar for sale I provide an accurate weight in the listing. It's convenient for both the potential buyer and myself. = Win/Win.
...and there's my $0.02.