It depends on the niche that you are into. If you are selling Amazon products or CPA offers, you don't need a list. For Clickbank niches, like weight loss, green energy, internet marketing etc, it is recommended that you start growing a list.

However, you can still make money from Clickbank niches and internet marketing niche by using SEO or PPC methods, that is by targeting product name keywords on Google.

Keep in mind that growing a list and making money from your list are two different things. What I mean here is, just because people subscribe to your list, it doesn't mean they will convert into buyers. The best method to grow your list is by selling your own product or collecting emails from other people's thank you page. You will get real buyers subscribing to your list, instead of freebie seekers.