It's an interesting question! I suppose if you consider it to be true, then it might be because - as some people here have already pointed out - many scientists see language-learning mainly as a tool, i.e. as something they need to give presentations at conferences, to read books and articles on their specific subject or, at most, to communicate with colleagues from abroad. And as a tool, most languages are quite unwieldy. Now, if you keep thinking "My goodness, why do they make it so complicated? It's so illogical! It could be so much easier if there were clear rules and no irregular verbs (or articles, cases or grammatical genders, as the case may be)", this will hinder rather than help you to learn a language. I think learning a language at least seems a lot easier if you're interested in learning it for the sake of the language, instead of learing it as the means to an end. Because then you'll be interested in or even fascinated by its quirks and irregularities, rather than being irritated by them. And I think it's been scientifically proven that your brain tends to retain information much more easily if you like it and find it interesting than if you think it's boring or even annoying - but then again I may have made that up, just to prove my point. ;)