Why is 有 used in 你的表有一点儿快?
你的表 (your watch) is the topic

有一点儿快 ( is a little bit fast) is the comment

in '有一点儿快',  '有' (having) indicates 'possession' of a condiction or ability, which is 'being faster than normal'

therefore, the literal translation of the sentence would be 'your watch is having a problem of being a little bit faster than normal'

[(topic) + (comment)] sentence structure is different from typical S+V+O structure like "你的表(subject) 行(verb) 快了 (adverb)"

Since 你的表有一点儿快 is a [(topic) + (comment)] structure, '一点儿快' describes something the watch possesses, therefore you need '有' to indicate this possession