They also reduce the ampage drawn from the battery amongst other things, making your battery last longer. I don’t think a cheap diy controller does this.
If you calibrate correctly, and maybe add a few more increments to allow for height and/or cold temperature to make it less sensitive, you shouldn’t get a problem. It’ll also save your pump pressure switch as it won’t be needed.
That’s my understanding of them anyway. I would struggle without them.