What are the main reasons for patent application abandonment?

According to MPEP 203.05, there are four main reasons for patent application abandonment:

1. Formal abandonment by the applicant or their representative
2. Failure of the applicant to take appropriate action during prosecution
3. Failure to pay the issue fee
4. For provisional applications, the passage of 12 months from the filing date

The MPEP states: An abandoned application is, inter alia, one which is removed from the Office docket of pending applications: (A) through formal abandonment by the applicant or by the attorney or agent of record; (B) through failure of applicant to take appropriate action at some stage in the prosecution of a nonprovisional application; (C) for failure to pay the issue fee (MPEP § 711 to § 711.05); or (D) in the case of a provisional application, no later than 12 months after the filing date of the provisional application.