Shrinkwrap did not use hashes and did not guarantee deterministic installs. Subdependencies could still end up as different versions.

Even the shrinkwrap file itself contained a lot of trash and generated massive diff noise. I had a file full of scripts to make the shrinkwrap file usable and even then we had (production!!!) issues due to changing subdeps. We reworked our build processes to zip & deploy the exact code that passed the tests to work around that, but it was still a massive pain that installs at different points in time would yield different trees.

When yarn came out, I deleted a folder full of hacky scripts, cut my install time by 60% and finally got deterministic installs. Needless to say, I was ecstatic.