Free plans suggest that your service is worth nothing, because you can give it away for free. That's not always acceptable, especially when dealing with larger B2B clients.
Yeah, I agree with the bigger enterprise clients. Sometimes it's hard to have a free version of software you're selling to these types of customers.
My point on the free plan is more like a trial where you get limited use, not giving away the entire thing for free. In interviewer.io's case I also want to be able to help smaller startups who might not be able to yet afford a paid plan at least use the product for the stage they are at.