I can literally build a Jenga tower with standard size Jenga blocks using a forklift (we have little competitions every so often)(unfortunately I can't show pics or videos otherwise it'd be a security incident)
Of course it's assuming that's how advanced propulsion tech works. But it is useful to try to detect, just in case that's how it actually turns out to work, no?
And if we detect something interesting, like a potential warp bubble collapse, well, that also gives us a strong hint that it's possible, helping us to direct research in the right path.
Detecting techno-signatures of aliens would be super useful for us.