I don't think the lockfile is a big problem (and I don't have enough experience with lockfile-based systems), but if you already have some other file that can serve the same purpose, isn't that nicer than having two? It also means you don't have to be confused about whether lockfiles should be committed to version control (apparently the answer is "not always", which is counter-intuitive to me).
You're supposed to commit it for applications, but omit it for libraries. Libraries declare the versions they're compatible with but they don't lock to specific releases.
In at least some packaging systems, committing the lock file for a library is useful so that the library maintainers use the same versions. (It's ignored by users of the library.)
