Barnes bullets makes some really great all copper bullets!!! ...so lead in bullets is not necessary, simply more cost effective..
A bullet is a tool to kill people with.
If a copper bullet is more accurate and deadly, by all means, we should use it instead of lead.
Now, if you want to make a case for depleted uranium bullets and a greater wounding/killing force, I would gladly agree.
Try an experiment... Shoot a 1/8" steel plate with a copper bullet, a lead bullet and a depleted uranium bullet from 50 yards... tell me which one works...