This is from an individual perspective, because Comcast/Spectrum/Three/ limit upload speed and capacity so thoroughly that it becomes impossible for people to complete verification in a reasonable time (a few days to a week or two).
Which, how's relevant again? Using extra disk space isn't going to make their verification faster. It can make their possible and probable future re-syncing faster though.
The network as a whole does not benefit from reduced bandwidth usage, it's those who run nodes from their house who stand to gain from such a reduction in bandwidth.
Granted. But, as I said, if someone doesn't want to spend a few hundreds of gigabytes for these extra benefits, helping the network bandwidth-wise is a very indirect incentive. (And if he does it, it's mostly going to be for his own benefit)
Nodes can upload both blocks and transactions.
My bad. Since
BIP159, pruned nodes can advertise themselves as having these few blocks:
Abstract
Define a service bit that allow pruned peers to signal their limited services
Before that, it was disabled by default (since 0.11.0):
For now, block pruning disables block relay. In the future, nodes with block pruning will at a minimum relay “new” blocks, meaning blocks that extend their active chain.