Celeron is a brand for simpletons and businesses.
Consumer A goes into a store and wants a laptop. The salesperson asks what they're going to do with it, and they respond with email, Facebook, and YouTube. The salesperson recommends a netbook, but no, netbooks are too slow, so they've heard. The salesperson recommends a notebook with an AMD processor, but no, Intel is better, so they've heard. The only thing left in the consumers price range is Celeron, and thus, another sale is made.
With businesses, these companies get stuck in ridiculous sales and service agreements with big names like HP or Dell. Company B needs 10,000 desktop computers. These are for marketing, finance, presentations, etc... Computer Retailer C recommends Celeron desktops, at the cheap cheap price of $1000/year 3-year leases. This is such a steal compared to $2000/year 4-year leases on "engineering" pcs with Core 2 processors that the order is immediately placed.
Really, I can't think of another scenario where a Celeron is ever purchased willingly.