Hi! The second example is actually the incorrect one. In your first example, the use of “why’d” is the contraction form of “why did” and used more in informal or casual speech, meaning I hear and use that form quite often. The question in its complete form would be, “Why did you call last night?” The second example is missing the word, “did” which as previously stated, is still present in the first example through the contraction, “‘d”. (“Why’d” is just a short way to say “why did”) To fix the second phrase you must simply add the word “did” before “you call” and then both phrases would be correct. You cannot have the second phrase without the word “did” before the pronoun and the verb. I hope this helps! :)

B. Pizz has given a good answer. "Why did you call last night?" - correct (standard) "Why'd you call last night?" - correct (casual) "Why you call last night?" - incorrect