I’m not a linguist, just an Ancient Egypt amateur geek, but it’s worth noting that hieroglyphs were the formal, monumental script—used on temples, tombs, statues, and religious texts. They’re beautifully drawn and symbolic, but slow to write (think carved calligraphy rather than everyday handwriting).

There were also cursive forms. Ancient Egyptian had three main writing systems used in different contexts: hieroglyphic (formal), hieratic (a handwritten cursive), and later demotic (even more simplified, for everyday administration and legal texts).

To your point, our germanic linguistics Prof (Elmer Antonsen) pointed out memorably that the futhark (runes) were essentially the roman-phoenician characters shaped to coordinate with the grain of wood.

That doesn't explain omitting vowels here. Whatever brevity you gain from omitting vowels is more than made up by the phonetic complements and determinatives you need to make up for their loss. Besides, individual Egyptian hieroglyphs tend to contain a lot of unnecessary detail. Look to hieratic if you want to see what the Egyptians did when writing required some efficiency.