That is a problem, a TOC▸ (ATW▸ ) locked into a 15 year contract since 2003 has seen a passenger growth of 75%. Franchises prevent TOCs being able to adapt to changing circumstances.
I'm not convinced that's always true.
Getting the 180s back wasn't in
FGW▸ 's franchise agreement at the time. Ordering a bunch of 170s wasn't in Central Trains' franchise agreement. And so on.
Shortages of available rolling stock are one thing, but when stock is available - and it sometimes is, as per Chiltern nabbing the 170s from
TPE▸ - franchises can and do take on extras, as long as (
AIUI▸ ) the franchise-holder can convince the
DfT» that there will be no impact on the subsidy profile.