[onion2k]

If output were stable then innovation would only be used to improve the efficiency of production. That would mean fewer jobs producing the same amount of stuff, which would lead to increased inequality (fewer people working and earning compared to people who aren't working). That doesn't sounds like a good thing to me.

The societal benefit of "infinite growth" is fully utilising the workforce. If an innovation reduces the number of people needed in a job we can try to grow a different part of the economy to use those people. Unless we can think of a different way to utilise people (eg universal basic income, negative income tax, free stuff for everyone, or something) growth is a useful mechanism to regulate society to an extent.

[coolaliasbro]

Output should never be stable in theory as people will not always need the same amounts of the same things. Optimally, output of consumer goods would dwindle if they were made to last as long as possible and convincing people to buy shit they don't need or really even want wasn't a key component of the economy. Also, the notion of "ways to use people" seaks directly to the alienation of labor central to capitalist systems.