If you don't collect addresses, your marketing effort is a one-shot wonder. You're making only one attempt per visitor to achieve a sale and then giving up.
As branding expert Rob Frankel says, people like buying from people they know, like and trust.
If you're not giving people a chance to get to know and trust you, don't be surprised if they don't buy.
If you're not collecting email addresses, you're seriously crippling your marketing. Remember how the big dot-coms poured buckets of money into banner advertising and TV advertising? Now they've finally realized that collecting email addresses is much better value.
It's getting harder and harder to do, because we're all deluged with spam and newsletters which don't provide the information we need. So get started now, before the competition becomes even stronger.
You may not want the commitment of publishing a weekly newsletter. Perhaps you don't believe you have the necessary skills. One option is to simply offer a monthly Update newsletter, telling people what's new on your site.
Perhaps you don't like the thought of being tied to a weekly or monthly publishing schedule. You don't have to be. You can publish irregularly, only when you feel you have something worth saying - or selling.