If stock prices get high enough, it becomes worthwhile for companies to issue more stock, thus injecting more capital. If they become low enough, and if the government doesn't interfere, it is beneficial for all shareholders to have the company buy back stock (shareholders who don't sell see the value of their shares increased because they are less diluted).
Nonetheless, it is very important to keep in mind that there is no universal benefit from having stock prices rise. It benefits sellers, but harms buyers.