In some cases the results of not having ligatures can look terribly bad. For example for fonts where the 'f' ends with what looks like a dot: if you put that kind of 'f' with an 'i' after it, the dot of the 'i' and the end of the preceding 'f' make for a very, very ugly artefact which looks like two dots connected to each others. Not only I find this ugly but also actually distracting. It depends on the font used, the kerning, etc.
This kind of uglyness due to the lack of ligature if not as noticeable on digital media, where we typically don't have the 1200+ dpi that print does and where, hence, you tend not to have these kind of 'f' (for example) because fonts have been hinted (or specifically chosen / created) not too have these issues.
I hope my explanation makes sense: I'm not a native english speaker but I did write and typeset myself about a dozen books (most with Quark XPress, one with LaTeX)... And they were all using ligatures IIRC (I should check for my LaTeX one: it's been a long time).
This kind of uglyness due to the lack of ligature if not as noticeable on digital media, where we typically don't have the 1200+ dpi that print does and where, hence, you tend not to have these kind of 'f' (for example) because fonts have been hinted (or specifically chosen / created) not too have these issues.
I hope my explanation makes sense: I'm not a native english speaker but I did write and typeset myself about a dozen books (most with Quark XPress, one with LaTeX)... And they were all using ligatures IIRC (I should check for my LaTeX one: it's been a long time).