• There is less risk in starting the relationship. You're not divvying up shares in a company or even paying a fixed salary. The only thing you stand to lose is the time spent figuring out the comp structure
• Founders don't have to open up quite as much about the business, and worry that their idea will be stolen/copied. This is partly because founders seeking salespeople will be further along (alpha version or later), and partly because there's less of a fear that a salesperson will start a copycat company than an engineer (because of skills, not intrinsic honesty).