Because the European Commission is "faceless, unfair and inefficient" and because the straitjacket of the Euro has enabled a few countries to benefit massively from exports denominated in a low rated currency where they would have struggled if their trading currency were based on their own economic performance
Germany and other euro countries had fantastic exporting economies long before the euro came along plus the £ has fallen in value by around 25% against the euro since 1999, yet the UK has not seen a boom in manufactured exports but has in services, much to the EU.
The precautionary principle is a brake on innovation
Is it? did it stop BioNtech inventing the worlds first RNA vaccine or the french rolling out a hi speed railway, the european space agency (not an EU thing) the euro fighter, super cars from Italy & Germany, Airbus, now a genuine rival to Boeing.
Seen the Milau bridge?
The EU commission does not have the reach many imagine, it might (or not) want to rule europe but it doesn't, in fact the freedom for scientists/engineers etc to travel freely around europe, actually helps europe compete, something uk universities have benefited greatly from, hence UK agreeing to pay into Horizon (but now with zero say)
The many and varied issues the UK faces, are nothing to do with the EU, they are fundamentally based on who we have voted for & the sovereign decisions we have made.... housing, training, transport, public services, health, education .... all under our control, to do as we please.