People develop favorites over the years, and those who really are in it for the photographs (read prints), value having access to materials that are consistent.
At the same time photography is also driven by a lot of propeller heads (like me), who like to try new things, and admire innovation. The new Ilford Art 300 paper, for example - it helps to keep the Ilford line of papers fresh. New product introductions may not be important to everyone, but it is to some, and for that reason it's important to at least try bringing news to this almost abandoned way of making photographs.
If you look at almost any company today, innovation and new products are, for the most part, their life blood. Cars and electronics, for example. While some value traditional things about these things, most people value having something new and exciting to look forward to.
Look at Ilford, they have been asked to come up with a Delta 25 film, for example, but ended up not being able to justify it. They came out with the Warmtone and Cooltone developers. Only the Warmtone made it due to market demand, but hey - they tried bringing something new, and they did! Kodak came out with the Ektar 100, which (if memory serves me right) is a derivative from movie film, new versions of both Portra 160 and 400. TMax 400 was improved only a couple of years ago, and what a fine film it is! Fuji came out with Velvia 100 (it isn't that long ago), and while they brought back Velvia 50, they still kept the 100 around.
I mean, why not? I work for a company that has managed to grow around 10% year over year for years now, with a slight dip in 2009 of only 6% or so. In a bad economy, and a highly volatile market (commercial construction), and the reason is attributed to new product introductions, at least as far as organic growth goes. It sends a sign that the company is strong, and worth investing hard earned cash, as well as time in.