An existing company making a new issue is kind of unusual because it dilutes the value of existing shares which is harmful to existing shareholders. generally a bad thing.
Selling Treasury stock does get new cash in the hands of the company, but usually that was because at some point the company had excess cash and invested it in it's own shares in the form of a buyback, less often the company is still holding shares from it's own IPO. It later needs the cash and re-sells the stock, hopefully at a better price.
I would argue though that the day to day trading of common stock on the open market is the more general rule not a "extremely specific case". Normally, if I go to make a trade in my account, it is not a new issue and would be a coincidence if it was at the time a company was selling treasury stock.
no argument in stock liquidity being a measure of confidence, but not really to the point I was addressing.
I wanted to mention liquidity because I (wrongfully) thought your post implied it wasn't particularly important; is indeed paramount for the stock market to work at all.
Technically and in the extremely specific case, yes, buying stock on the market doesn't create jobs for anyone. However, the liquidity of stock in the aggregate is one part of the confidence of the financial system. Upon IPO, buyers of the stock need to know they can sell their stock on the market after it fulfills their objectives.