Because the citation form you learned is not the form anybody uses inside a sentence. Thai reduces heavily, it reduces predictably, and the reduced form is not sloppiness. It is the normal register, and the careful form is the marked one.
You have been building recognition against a version of each word that occurs mainly in classrooms.
What actually happens
Unstressed first syllables of long words lose their vowel or vanish. มหาวิทยาลัย is not delivered as six clear syllables at conversational speed by anyone.
ครับ becomes คับ: the ร is simply not there. This is not lazy, it is what Bangkok does, and คับ is common enough to be written.
อย่างไร has been ยังไง in speech for so long that ยังไง is the real word and อย่างไร is the written ghost of it. The same has happened to several others you were taught in their full form.
- ครับkʰráp
as written
- คับkʰáp
as said
- อย่างไรjàːŋ.raj
how (written)
- ยังไงjaŋ.ŋaj
how (spoken, and the one you should use)
- ไม่เป็นไรmâj.pen.raj
never mind
three syllables on paper, closer to two at speed
The ร in general
In a consonant cluster, fast Central Thai routinely drops the ร or turns it into ล. That is not a regional accent to be avoided: it is Bangkok, and it is the majority of what you will hear.
So the script teaches you a form you will rarely hear, and your ears teach you a form you cannot spell. You need both, and neither one is the wrong version.
What to do about it
Stop trying to hear words and start hearing phrases. A word learned alone has to be recognised alone, and it almost never occurs alone.
This is the argument for the sentence cards taking over from the vocabulary deck in month two: the unit that survives fast speech is the phrase, because the reductions happen at phrase boundaries and inside them, not inside the dictionary.