I've personally tuned a lot of software that ran better with a constant growth factor than an exponential one.

The problem with exponential growth is that, if you're doing a thing that is (kn)+1 bytes, where n is the growth factor and n is a decently large number, you end up with k(kn) bytes, which leaves k^2 * n - kn - 1 bytes useless. Depending on the value of k that can be a big chunk.

Particularly in situations where you're memory constrained and creating long-running processes, adding some-large-percentage of your buffer in empty overhead just wastes resources. It's better to spend the extra allocations in the first minute, and then have it run for a day, than have the first minute be faster and have it take 36 hours because it can't fit the working set into memory.