Because the line does need to be drawn somewhere. You can't just go out, cause harm to someone, and then claim "Oh, that harm was done by my company, not me personally. Incidentally, my company only has like $20 in assets for you to recover."
The paperwork also doesn't entirely grant you the limited liability. You need to actually operate the company as a separate entity from yourself. If you "piece the veil" between individual and company, you may not be able to claim limited liability in court.
See 2 comments ago. Nobody except the ultra rich could afford to go into business if it meant risking all of their personal assets.
And like already mentioned: it's not less liability, it's separate liability. Misconduct as a business (which may not even be the owner's fault, it could be an employee's) can risk all of the business assets, but not personal assets owned outside the business.