This. The EU is made up of countries that would prefer the UK to remain.
Example: France- doesn't want huge delays at Calais or disruption to their own services caused by ports and Eurostar being affected. They have a vested interest.
All of the other 27 countries ALSO have vested interests- either for UK citizens in their country (that they likely don't really care about, more likely their economy and services that would be affected if they weren't allowed to stay) or their own citizens in the UK. Ireland obviously has an interest in the NI border. Spain- Gibraltar. Everywhere- tourism.
It would be easier for all 27 if the UK stayed. They probably don't give a crap about the UK and don't care what it does. They want to serve their own countries interests. Which are improved if GB stay in the EU.