Big ships move slowly

Richard Rumelt, in Good Strategy, Bad Strategy:

It takes years for a formerly regulated company, or a former monopolist, to wring excess staff expense and other costs out of its system and to stop its accountants from making arbitrary allocations of overhead expenses to activities and products.

In the meantime, these mental and accounting biases mean that such companies can be expected to wind down some product lines that are actually profitable and continue to invest in some products and activities that offer no real returns.