Ask HN: Why does OCR still suck with handwriting?

I wanted to digitize the notes that my classmate gave me yesterday. I used Google Lens to scan them and convert them into text. However, it did not work well. It could not recognize many words and letters in the handwriting. I was disappointed because I heard that OCR technology is very accurate and reliable. But it seems that it only works well with screenshots and books. Handwritten notes are still a challenge for it. Why? Why does OCR still suck with handwriting? Is there something I am missing?