It's a never ending cycle. Tweets, likes, updates, posts, comments and any other way to indicate "activity" on the social sites.
From anything that demonstrates a person having a pulse, just about everyone is expected to have a presence on social media.
It doesn't matter which platform you prefer as long as you remain engaged to those who are following your activity on that particular channel. For those who choose not to participate, are they really missing out on anything?
It all depends.
If you are trying to grow your business, it makes sense to be online and reactive to the messages that are sent to you. If you choose to ignore those messages, that is an even larger signal to your potential customers that you aren't going to be responsive to their needs.
It doesn't mean you have to live attached to your online profiles. Most smartphones have ways to notify you the moment someone replies to a post of yours. Take advantage of this service so that you can always appear to be online to your audience.
So what social media is best for you?
There are no set rules to this, but traditionally, Facebook drives the most traffic, followed by Twitter and Youtube. But, I also know of people running their entire business on Instagram, making over 40k per month, so it's all dependent on your audience.
Like all things, try them all and see what works the best, you never know what will be the one that sets you on a great path to success.