One of the challenges with small businesses is that most of the time, you are asking a business owner to take money out of their savings account and give it to you in exchange for something they don’t really understand.
It requires an enormous amount of work on your behalf to build that trust, and the client is on tenterhooks most of the time because they have so much skin in the game.
Larger clients are usually spending a budget that has been allocated well in advance, and have more realistic expectations regarding outcomes.
Most of the time you will also be working with a project manager who has more experience than the average small business owner.
Larger organizations like dealing with small teams or solo developers because they generally work faster and are more agile.