This is generally true. I had a technical cofounder for the first 4 years or so, but once our tools were built it was less clear what his ongoing role would be. This is because at that point, our focus turned to licensing our (patented) technology to businesses. We still have B2C customers who use the tools that he originally built (and which have been updated by contractors after he left), but now the vast majority…
What so the person who "provided a lot of value in getting us to where we are" got ditched in the end? Is that your story? Use people and then chuck them to the curb once everything u need has been extracted?
Technologists beware -- some business co-founders will treat you honestly and you'll be paid fairly. And some will not. You need to read this comment and realize that both outcomes are possibles, especially once lawyers, VCs, and other business people get into the mix.