This is a pretty obvious reason. If you're trying to market something today, you'll have to get it onto the internet. Everyone else in your market is already on the internet, or soon will be. A site could be your main marketing vehicle, or just complimentary to whatever existing system you already have. There's almost no kind of business that can't benefit from a website.
The exact kind of site you require depends on what you sell, and how. It may be that you need a site with a catalog, so all your products can be listed and people know what's for sale. It could be that you need a site to list information, manuals, FAQs, or white papers.
Regardless, you can create it yourself or hire someone to do it for you. It's up to you.
2. You have something to say.
Maybe you just want to prove a point. You're not alone: there are many opinionated voices on the internet. Why not add yours?
Regardless of whether your message is a formal declaration of your cause or just fun communications, there's room for your voice online.
3. You should show people you're good at what you do.
If you're an employee, it may be that you don't have anything to directly sell. Maybe you don't have a voice that wants to be heard, either. But your job is very important, and you want to get the most you can out of it.
What better way to prove your worth than to have your own site? You'll be able to point to months or years of material that you have written. This will demonstrate that you are serious about your field.
It has never been more beneficial to have a website than now.
