If they're growing revenues at a slow pace – or have a low profit margin – it's more like looking in through an opaque window at bankers doing less with your money than other bankers could. You'd much rather withdraw that money and invest it nextdoor.
Also worth noting that "no rush to IPO" is not the same as "never IPO". As a VC, you're investing with the understanding that an exit is many, many years away (if it ever comes at all), on the hope that this longer time horizon gives founders the flexibility to do crazy unicorn stuff. I can imagine a CEO telling the VCs "hey, we're going to wait an extra 5 years to IPO, but that's because we want to do crazy 10x return stuff that's difficult to pull off as a public company because of required SEC filings, activist shareholders, etc.".