It's not the policy in itself that seems strange to me, it's the fact that it is also applied to IT goods and services.
Basically, the policy relies on the two ideas below:
- With fewer providers, you can purchase more of the same and negotiate a better price next time.
- With fewer providers, you can establish true relations of trust and avoid gaps between what's asked and what's provided.
However it relies on the three following assumptions:
- Purchasing at a specific provider will impact the price of other providers only downwards, and that will be only a small impact. This is wrong in IT, because the cost of moving to another provider is very high, because of software and hardware incompatibilities.
- You can negotiate with providers. This is wrong in IT, because you're always speaking with big international companies. If they allow you to negotiate, that's within an already well-thought area.
- A true relation of trust brings a really better service from the providers. This is wrong in IT, because the hardest part is always the exploitation of a product or service, not its purchase. Good relation with the provider only marginally increases quality.
Knowing that you can't move anymore, the provider you chose has the hands free to increase prices.
That's what happens in reality:
So, to my mind, the policy of reducing the number of providers is detrimental to IT services.
However, the real difficulty coming from the integration of very complex technologies, very differently thought, born in in very different companies or universities, and best manipulated by people outside your company (either service providers or editors), I think it is a good policy to maintain a list of technologies that you use, the (in)compatibility links between them and to think carefully before adding one to the list.