QUORA ANSWER by Siddharth Bhattacharya:
People find maths difficult because it is inherently difficult. Or- the time to realize one doesn't understand Math is much lesser than any other discipline.
I've graduated with degree in Mathematics & Computing alongside completing various courses in humanities- economics, literature, sociology. Nevertheless I'd prefer encountering a new topic/academic work in the latter for one in maths requires much more endurance and struggle. Why? Because Mathematics is too difficult to relate to. (I mean advanced mathematics, not basic arithmetic) Comparing to a subject like music, history, literature- we tend to have some ideas or opinions regarding them. Although it may bias our reading, it eases as well for it helps in association. Contrarily when we sit with Maths, we're dealing with something entirely new whose practical implications in our daily life are hard to imagine. If we draw a hierarchy tree, Maths would sit atop as it's concepts get used in 'applied fields'. The farther anything moves from reality, the more difficult it becomes to comprehend.
Even after studying advanced maths for 5 years, I'd struggle to define topology, while I can voice opinions on state-of-law, events in history and implications, intent of writers through protagonists primarily due to the subjective nature of these subjects. If I state "World War 2 was won by Germany" then I am wrong, but any further discussions on the topic "Was US right in bombing Japan?" to even the most extreme question considered "Was H****r doing the right thing" can have diverse opinions. Although these views maybe kiddish, there is a place for them motivating students to pursue further for they can connect with it. Contrarily the objectivity of Maths makes it much tougher. Everything has a definite answer. Is "Hausdorff space compact?", "Is this system deterministic or probable? If the latter, what is the probability?" There's no "maybe it's probabilistic system". There's no place for 'opinions' and those who missed the basics of the subject would fail to understand the successive things entirely.
Source : https://www.quora.com/Why-is-mathematics-so-hard-1