Without coming down on either side, the simple answer here is because the funding company would be ahead of competitors.
In high-tech markets, pioneers often develop durable leads (Apple, Microsoft, Oracle, Amazon, etc.). There's a huge business advantage to having the IP + the team that developed that IP in one place.
Conversely, handing over IP alone doesn't build a business. For example, Tesla could give away all their private IP for the Model 3 and it would still take a lot of investment for a competitor to arrive at a parity offering (which would be years behind, because Tesla's teams haven't stopped). Because the product is much more than a sum of the basic research.
In high-tech markets, pioneers often develop durable leads (Apple, Microsoft, Oracle, Amazon, etc.). There's a huge business advantage to having the IP + the team that developed that IP in one place.
Conversely, handing over IP alone doesn't build a business. For example, Tesla could give away all their private IP for the Model 3 and it would still take a lot of investment for a competitor to arrive at a parity offering (which would be years behind, because Tesla's teams haven't stopped). Because the product is much more than a sum of the basic research.