Your website is an extension of your business, it should provide information to existing and potential clients/customers, it should give people opportunities to learn more about your offerings and to connect with you. There is not a business type that I can think of that should not have a website - it is like asking should I have a business name, ABN and accounting software. It is a reflection of how professional and serious you are about building a successful business.
The world wide web has become a very confusing place to be part of - and it is possible to sink lot's of money in without seeing any return. You need to understand how it works, or partner with someone who understands. It is not a fad and it is not going away - it is growing - and if your business is to survive you need a website.
You have a Facebook page - that is enough right? Here is the thing - you do not own your Facebook page, the content or the likers. You have no control over Facebook changing (improving?) the rules. You can have 2000 likers but only getting an engagement of 30. It is the same with all of the social media platforms - they are important - but your website gives you 100% control - all the time. Or it should.
If you have a website and not sure who owns your domain name, where it is hosted or at minimum how to do content updates - then ask questions and learn. Websites can be a mere page with basic information - or they can be gigantic with complete e-commerce systems built into them - the size depends on your businesses needs.
Website developers have been creating websites since forever - many of them have used code to create and update sites - these guys (and gals) understand about widgets, components, modules and code - so some things are best left to the pros. With great CMS available today there is no reason you can't learn how to do content updates yourself - for many it is not much harder than using word.
Your website presence does not need to be huge, it does need to work for your business however, check out your competitors and what they are doing and review your site regularly. Ensure you have google analytics on your site so you can track visits to your site - how else are you going to determine what works and what doesn't?
Before you say you do not need a website, look at what your competitors are doing and have a think about how a website could help you 'do' your business. It should be working with you. A website will at the end of the day build trust with the people that you meet - if they don't do business with you, they may just refer someone to you who will.
Let Visionary help you with a Digital Review for your business (FREE) - follow this link