If the next logical step for Twilio is an IPO, does that mean that they're not profitable? If they are profitable, why is an IPO the logical next step, does an IPO provide specific value to the company (or any company) beyond financing?
On the web, there are no longer barriers to entry.
If I'm an enterprise, I'll go with Twilio over some 2 week old startup because of its proven track record and the likelihood of being around in a year.
I hate to use this example because its a bit cliche but Google entered late into a field of established players and won. Microsoft beat IBM (this one applies only to the PC, I know IBM is still a force to be reckoned with). Stripe, Balanced, and Square are able to compete with PayPal for accepting payments. I know these arent all enterprise-specific but I didn't take the parent's comment to be about enterprise only.
What you'd do as an enterprise and what real enterprises would do are two different things.