Should you offer support right a way?

I was thinking about a conversation I had recently with an investor in many open source companies. He was saying that open source startups need to start charging for something sooner.

Which made me think: Why don’t more startups offer paid support as soon as their open source project is live? I don’t mean like hourly services contracts, but rather support SLAs similar to the ones you’d see on the enterprise editions. There’s no reason you can’t offer that — and charge good money for it — as soon as you have a functional open source project. What’s more, this is a technique used by many bootstrapped open source companies — release awesome open source project, offer support contracts as an insurance policy for organizations that need it.

Is there a reason I don’t see many startups doing this? Am I the dense one here?