Because the term "lobbying" is overinclusive to the point of being useless. 90% of lobbying is not only benign, it's necessary to the functioning of a republic. It involves people likely to be affected by the law telling lawmakers their thoughts. These people can be companies. They are also, very frequently, interest groups, nonprofits and individual voters.
This is why "let's ban lobbying" is a siren call. If you have representative democracy, you will have influence peddling, i.e. lobbying. "Let's ban corporate lobbying" becomes more tangible, but keep in mind this means you're basically banning every business that can't fly its employees to D.C. from being able to fully communicate with lawmakers. (It also leaves untouched the community organizing side of lobbying, arguably its most potent part, and would probably fall afoul of the First Amendment.)
The unfortunate effect of this overinclusiveness is it papers over the bad stuff. The lack of enforcement around campaigns coördinating with PACs. Board seats and cushy jobs offered to former lawmakers. Campaign donations from non-natural persons. This is the stuff I think people are actually offended by. But it's currently too technical for the base that wants to "ban lobbying."
TL; DR If you want to push the needle on this issue, drop the idea that lobbying is bad. If you've donated to the EFF, you've hired a lobbyist. If you've called your Congressperson, you've lobbied.