Ask HN: SSD File Transfer Speeds

Why do file transfer speed run at 1/5th to 1/10th the quoted maximum read and write speeds? Researching online, you can get an SSD that supports 7,000+ MB/s read/write speeds and top out at 3,000MB/s for a USB4 enclosure. But I only find people getting 1GB/s transfer speeds for regular setups (without enclosure). Why are benchmarks and file transfer speeds so different? Are there any sites that track transfer speeds? Where would you start debugging this?