The whole reason to have leap seconds is _because of astronomy_. If we removed the leap second from civil time keeping, astronomers would still maintain it,

The whole reason to have leap seconds is _because of astronomy_. If we removed the leap second from civil time keeping, astronomers would still maintain it, because they want their observations across several decades or even centuries to use a time scale that's linked to the rotation of the earth. That's because their telescopes are bolted to earth. So when the rotation rate changes the time at which certain features appear in the telescope also change. They might consider using a higher precision version and make smaller updates more often but since the rate is not perfectly predictable and can be altered by local events on earth and you want all astronomers on earth to agree to the current value the second is the most reasonable unit of change for them to use.