Earlier quoted context omitted.
The XPS was their higher end answer to the unibody Macbooks a few years back, and peer with Lenovo's Thinkpad X-series. The Inspiron line is a "cheap is expensive" trap for consumers, you can't blame people if they judge the whole company for their mass-consumption offering when its cheap build breaks at the hinges for everybody.
Frankly, if they're cutting corners on one product to the point it affects their brand image, they're probably cutting corners on all of them. This is one thing Apple gets right, their products are solid all the way down to the low end (iPhone SE et al). (After reading further I see others have made the same point. Oops.)
But I do agree with your overall point; back when I worked at a computer store people would come in to buy a laptop, and they wouldn't want a HP – even when that was actually a good model and a good fit for their needs – because they had a bad experience with a HP printer. I think that's actually pretty fair too, although I usually explained that the people who design the HP printers most likely never even talked to the people who design the HP laptops, and that even within $brand laptops there are are huge fundamental differences.
I suppose that overall, on balance, the brand recognition of "Dell" or "HP" outweighs the negative associations people have across the product range.