What is the #1 reason users drop off from a SaaS signup page?

While building our free invoicing tool, we noticed a huge drop-off whenever users faced complex auth flows or unexpected paywalls.

In your experience, what hurts conversion rates the most:

1. Too many form fields

2. Social login warnings/friction

3. Lack of instant value before signup

Would love to hear how you solved this in your ow

n products!