The fig leaf of an "existing design" is often used for new procurement because Congress is less likely to interfere with political considerations if it is viewe

The fig leaf of an "existing design" is often used for new procurement because Congress is less likely to interfere with political considerations if it is viewed as an upgrade instead of a new system, under the theory that working within the constraints of an existing system limit flexibility with respect to Congressional politicking. Upgrades are also assumed to be cheaper than new designs, whether they are or not. The boundaries are fuzzy but there are many examples of new systems packaged as upgraded old systems for the sake of procurement efficiency.