If you are in the business of Internet Marketing, you can choose not to use an autoresponder. You can also choose to throw money out of the windows, or roll it in neat little bundles and flush it down the toilet.
Whichever way you use to bring traffic to your website, it is costing you something. If you use Google AdWords or an equivalent, competing service, then it is costing you real money. If you do anything else, then it is costing you TIME.
Now think about a normal one-hour web surfing session, one of which you probably go on every single day. Think about all the websites you visit. All the webmasters of all those websites planned, planned and spend money – somehow – to get you to visit them, like them, maybe bookmark the site, and eventually return and buy something. So tell me, how often do you do so? I am willing to bet that 99% of the time, you leave a website, not having bought anything and never planning to ever return to do so.
Having an autoresponder gives you a second chance with your visitors, who are your customers. For a million different reason your visitors may not be ready to buy at the exact moment they are on your website – few ever are, which is the reason that conversion rates on direct unsolicited traffic is so dismally low.
If you do not have an autoresponder, then every time a customer leaves your website, all the money or effort you spend, one way or the other, is gone forever.
It's like the old brick-and-mortar business adage: "Do you have any Idea how much it costs to make the phone ring?"
That's what the owner says to the unmotivated employee who's not too quick to pick up the phone.
If you do not have an autoresponder, then not only are you letting the phone ring without picking up, but you do not even have an answering machine!