So their target audience is developers that are incapable of installing their own tools and that are cool with the cheap look and flimsy build quality of Dell laptops.
Unfortunately, that market actually exists, and nine out of ten times that lack of caring for quality is reflected in their work.
You won't run the risk of buying a notebook, install Linux, find that driver xyz doesn't work, then find the store won't take it back because reinstalling the os voids warranty. And waste money. This is a big risk when shopping for Linux laptops. Specially for cheaper brands that you can't easily find online reports about whether it works or not.
That's why you should make a disk image before you wipe Windows. Plug in a Linux Live USB, use dd + gzip to create a bit-for-bit copy of your hard drive (it should compress well because there's no data on the machine), keep the copy in an external hard drive, and then wipe the internal hard drive. Nobody at Best Buy will know what you did.
Unfortunately, that market actually exists, and nine out of ten times that lack of caring for quality is reflected in their work.