Absolutely you should. One frustration of search consultants, recruiters, internal talent acquisition teams and HR departments alike is the volume of unclear, unspecific, and unsuitable job applications we all receive. Especially right now, when so many are seeking new pastures. Firstly, please don't apply to jobs you just don't have at least 70% of the requested criteria for. Recruiters and HR departments often get criticized, rightly so, for not replying to job applications. But on the flip side it's hugely frustrating and time consuming to have to reply to hundreds of 'way off' job applications. Just because it's easy to do something, it doesn't mean you should. Think before you hit the 'easy apply' button. 

Secondly, given the volume of applications, the unsuitability of most, and the bland and generic nature of many, you do yourself a huge favour by being thoughtful and specific. I don't mean use coloured fonts, info-graphics and gimmicks (please), I mean be thoughtful of why you applied, and respectful of the company you've applied to. Show you took time, researched the company, the role, and thought about why you'd be a good fit. Write that in a cover letter. 

Before applying, think, research, write, you'll have a far better, and hopefully far more successful job search.

David