/ Why /

I could delve into the different problems caused by URL shorteners here, but someone (actually two people) already did it much better than me: Martin Georgiev and Vitaly Shmatikov published a paper in 2016 titled "Gone in Six Characters: Short URLs Considered Harmful for Cloud Services."

If you want to delve into the negative aspects that arise from the use of URL shorteners, I recommend reading the aforementioned paper: https://arxiv.org/pdf/1604.02734v1.pdf