Have you ever caught yourself with a long list of specialisms - or noticed it with others in business maybe? Anything longer than 2 or 3 things means you are probably not a specialist, you are a generalist who turns your hand to anything, a jack of all trades and master of none. And your potential clients, the people you are marketing yourself to, will notice this. If someone genuinely wants a specialist to do some work for them, guess what - they'll look for a specialist. They'll look for the person who says "I can do this one thing and I can do it for you incredibly well because this is what I am an expert at doing. I am a specialist." My experience from my early days in business, when I was trying to be all things for all people, suggests that when clients see that you 'specialise' in a lot of things, then they are likely to have one expectation - you will be cheap!
Is that what you want? Do you want your ideal client to take one look at you and say "yup, we'll go with that one because they're cheap." Or worse still "We won't bother going with them, they are too generalist and too cheap to be able to deliver the quality we require." I know I don't.
As a specialist, clients expect you to be an expert in your field - are you an expert? If you're not yet there as an expert what can you do now to become the experct, what will you do to be the trusted specialist?
So, do you really want to be a specialist? Or are you content attempting to be all things to all people? It's a simple choice.