The most obvious answer is that they are written in a different language: Accountant.

You probably don’t speak accountant very well. And you worry that getting this grant is going to come down to how well you speak accountant. Or that you’ll say something in accountant that doesn’t mean what you think it means.
Dig deeper though and you’ll find that budgets are about values. Devoting resources to something indicates value.

Budgets often make you confront the differences between your values and the values of the organization who is giving you the money, whether that is your employer or an external research funder.