I can see it from both sides but am
at the word hate in the thread's heading, such a strong word and surely far out of proportion to the problem described.
I have a system when packing my shopping so, depending what I've bought, may say "no" to a request from a charity bag packer (but donate some change anyway).
I also raise money for an Alzheimers charity by bag packing and am very much aware that some shoppers prefer to be left to deal with their own shopping and that's fine, I'll step back, out of the way. I don't care whether people donate nothing, a penny or a pound; I am raising awareness of our charity too and have had much positive feedback from shoppers.
I also do the tin collection thing by the entrance but stand to the side so I can be seen but am not in the way. I never shake the tin (I don't think you're supposed to anyway), and don't engage eye contact with shoppers, just wait for them to approach me if they want to donate.
That is how tin collectors should behave so they don't make people feel guilty for not donating.
I totally agree with the 'unloading the trolley onto the conveyor belt' idea, and if we have enough volunteers I would like to offer that service in future.
Other ways we raise money include running book/jigsaw stalls, but the bag packing raises far more.