Edit: This question attracted way more interest than I hoped for! I will need some time to go through the comments in the next days, thanks for your efforts everyone. One thing I could grasp from the answers already - it seems to be complicated. There is no one fits all answer.
Under capitalism, it seems companies always need to grow bigger. Why can’t they just say, okay, we have 100 employees and produce a nice product for a specific market and that’s fine?
Or is this only a US megacorp thing where they need to grow to satisfy their shareholders?
Let’s ignore that most of the times the small companies get bought by the large ones.
I guess it’s mostly because companies that don’t try to grow are eventually pushed into irrelevance by companies that do. So most companies you hear about are growth oriented.
In some sense it can be good for consumers. If you have a nice idea for consumers, it’s good that you are able to reach more of them or become more efficient in doing so.
Also, to start a business you need money. You can get money from investors, but they expect either interests on the loan, or that you grow so that their share is worth more. The latter is attractive, because you don’t have to pay interests that can weigh your company down. But then the value of your company is almost defined by it’s potential for growth. If you then decide not to grow anymore, this will tank the value of the company, and you might be stuck with a huge pile of stinking debt.