Astronomers Detect a Possible Signature of Life on a Distant Planet

If life evolves on a planet with only oceans, no surface, imagine how much longer it would take to discover rockets that can leave the planet.

Like if there was no surface on earth, and only fish, there must be some very significant reason for advanced fish to even want to leave the water, let alone the atmosphere

It would probably be useful for high speed travel. Speedboats can go a lot faster than submarines. Airplanes can go even faster, but they might be a bit impractical since they'd have to be full of water.

Also radio communications since radio travels much better through air than through water. Of course, they could just build antennas underwater and then float them above the surface to use them.

Navigating by the stars would be really useful, and for that you need to be able to see above the surface. I guess you don't need to go above the surface. A periscope would do the trick.

It might also be useful for energy generation. Wind power if the wind is stronger than ocean currents. Or solar because the light is stronger.