[hyperpallium]

It's easier to observe bigger objects than smaller objects.

Bigger objects have greater gravity than smaller objects, therefore are more spheroid.

As we get better at observing, we'll see more objects that are less spheroid.

[tempestn]

At least in the case of Oumuamua though, being non-spheroid wasn't really the weird thing about it. It was that it exhibited comet-like acceleration, without any visible off-gassing, and without breaking up as it passed the sun, as a comet would be expected to do. Also the fact that from our current understanding, it is much more likely for a comet to be ejected from a solar system than an asteroid, so it's surprising (not impossible, certainly, but unlikely) that the first interstellar object was more like an asteroid.

[hyperpallium]

Fair enough!