Actually, unless you're deliberately looking at the companies who like to invent their own proprietariness, they're more likely to have standard connectors and protocols; consider laptop displays, for example. The ones designing the laptop want to be able to use displays from different manufacturers, and the display manufacturers want their products usable in as many laptops as possible. This leads to standards, both normative and de-facto, and there being only a small number of variations.

I'm not as familiar with mobile device displays but given that standards like MIPI DSI exist, I suspect it's a similar situation.