Not sure if it's still the case but if I recall correctly, the majority of the bitcoin maintainers are employed by one company... so not sure there's an incentive for them.
Its probably more than one company. but even then, lets say that it was one company, shouldnt decentralized,open protocols have open specs to help create more clients?
Yes of course they should, but if core development is isolated to one or two companies, then they're not incentivized to produce these open specs so that they can maintain control, because they are also building businesses around these protocols. Another question: Is a protocol truly decentralized if its development is centralized?