My reasons are similar to the above, really.
No one has claimed that the EU is perfect, but I strongly believe we are better off as an EU member with an equal voice and a vote, than as a sidekick to the USA, China or Russia. We are no longer a superpower and the specific set of circumstances that enabled us to be one (for a while), no longer exist. We did retain a disproportionate amount of influence on the world stage, but this is ebbing away now.
We will never get a better deal than the one we currently have with the EU, and leaving won’t just make us poorer, but weaker, with less influence and bargaining power.
I don’t want to see US healthcare companies take over the NHS (and believe me, they have been trying to force their way in for years).
I don’t want to see our food safety laws, employment rights, health and safety legislation, environmental protection laws and access to healthcare reduced to US standards for the sake of a trade deal. The EU has done much to protect us from our own politicians.
I want my child to have the option to live, work, study and retire in any of 28 countries and not be stuck in the UK regardless of how the above pans out.
I want EU freedom of movement to continue to enrich this country (and not just financially). I’m particularly concerned about the numbers of healthcare workers who have left. Why would they want to stay where their spouses and children aren’t welcome? How will the NHS cope without them?
I want the UK to continue to play a key role in international research projects.
I don’t want the fragile peace in Northern Ireland to be threatened.
I don’t want the UK to gradually decline, while disaster capitalists pick over our remaining assets and distract us by scapegoating foreigners/the EU/the poor/young people/remainers. When will we ever learn?