Given an infinite time horizon why not invest in 100% equities?

Bonds seem foolish unless you are planning to withdraw funds within the next 5 to 10 years. Is there any other reason for bond allocation? Do bonds provide that much utility when rebalancing during a downturn? I don’t find that argument compelling when you have no intention of selling during a correction.

When the market crashes, just buy more…. What am I missing?