Egg-zachly!
I was talking about this with my cousin a few months ago. He is also my barber and has an Android phone and tablet. When it was rumored that Google was going to have "multiple" OEM's manufacturing their own "Nexus" phones this year, I mentioned that maybe what they are going for is a "brand" that is recognizable by the masses. Samsung has a smash hit on their hands by branding their "Galaxy" line of phones as their top-of-the-line phone. This is very important to the average, uninformed consumer.
Apple has one product of each type. Each year they release one new product of each type, only differing by relatively simple things like storage size and color. They don't really have multiple models and brand lines. So it's easy for the consumer to know which model they want.
Android has 1,000 handsets. Samsung makes a bunch, HTC makes a bunch. How is a consumer to know whether the Nexus S, Wildfire, One X, Inspire, RAZR or whateverthefunk are good phones? Which one is "best?" Which one should I buy? For Samsung, it's easy. The Galaxy line. That's the "best." Each year some consumers eagerly anticipate the announcement of the new Galaxy, even though Samsung still makes other phones.
HTC learned the hard way last year. Released a bunch of phones that were all pretty solid/good (save for a couple) as well as some low-range phones. What happens? The consumer does get confused to a certain extent. They saw what Samsung has done with "Galaxy" and decided to brand their phones for this year and cut back on models. Now what do they have? The "One _" line. It helps.
That is what Google is doing with the Nexus. It's becoming an alternative brand for the pure Google experience. It's the right way to go. More Nexus devices is also more win for us. Two years ago, I thought I'd never have the chance to get another pure Google device again because of my carrier (Verizon). Now, I truly feel like I have options.