The key word here is "pressured". There is no pressure to perform or participate in a hackathon. You can work on your own pace, or choose to dropout. Almost all of the people who participate do so because of their interest and not to win a trophy or some cash.
I guess you haven't had the pleasure of participating in monthly workplace "hackathons". Of course participation is optional, but it can look good on your promotion case wink-wink nudge-nudge.
I think hackathons could be fun but they should either be done independently from a company or do something that's not of any direct value to the company but something fun.