The short answer is that visa numbers are limited and there’s a substantial waitlist.
Congress capped the number of U visas at 10,000 per year (INA § 214(p)(2); 8 C.F.R. § 214.14(d)(1)). This means that only 10,000 applicants may be granted U visas each fiscal year. Only principal applicants (U-1) are counted toward the 10,000 visa cap. Derivatives (U-2, U-3, U-4, and U-5) are not counted towards the cap. A backlog has developed because the demand for U visas exceeds the supply.
If you apply for a U visa today, you can expect to wait at least nine months for USCIS to determine whether...