[jdbernard]

> but the second one doesn’t, the vowel is still there!

Isn't the "a" in "have" elided along with the "h?"

Shouldn't've Should not have

What am I missing?

[jack09268]

Even though the vowel "a" is dropped from the spelling, if you actually say it out loud, you do pronounce a vowel sound when you get to that spot in the word, something like "shouldn'tuv", whereas the "o" in "not" is dropped from both the spelling and the pronounciation.

[SAI_Peregrinus]

The pronounced vowel is different than the 'a' in 'have'. And the "h" is definitely elided.