The above is an interesting position and one which I have to say isn’t as easy nor clear cut a case to determine. I argue it is all about getting into this argument to be honest, if only to answer the question.
The concern is that a well sold and maintained product is often repackaged and sold in a more innovative way (the innovation is in the sales cycle, not the product development). This is something that with a tech hat, I tend to abhor, but at the same time I totally understand it commercially. In addition, there is a concern all companies face, and Microsoft suffered from. Straddling the innovators dilemma too quickly. The change of the Windows 7 to Windows 8 Start Screen was slated and this was a really off-putting change to end-users.
I’ve seen companies who have sold the same product into different markets (somehow) which have been on their product portfolio for 35 years, never mind 20 and whilst I absolutely agree with your principle of continued innovation, when it is part of the core revenue stream, the product has both got to be maintained and oddly, protected.
The side-effect of that legacy maintenance, which definitely isn’t ideal, is a coupling and ever increasing dependence on the legacy product, not only within the company, but at the company’s client base too.