Cycleon
the main reason for me to do so: i don't like gear on the outside of the needle. Sometimes sticking the needle in and i just felt the gear. That's way i decided to stick myself with a clean needle and save some drops as well, since it is possible.
solidspine,
This has nothing to do about buying more gear. When i shoot 2 cc's Primo, it makes no difference how i do it. I still only use 2 amps.
More dangerous is:
mixing water and oil roids
using a 1 1/2 needle and not going in fully
not using both hands when injecting
buying gear from an unknow source