How do I convince my company not to include vendors when commiting?

I just started a new job as a Magento developer.

When cloning a project that took longer than expected, I discovered all of the vendors were committed on our VCS.

I asked the CTO and he said they started doing this because they had an issue with modules versions and composer at some point, but they didn’t go more in depth.

I know this is definitely not good practice, but is it something I need to lose time over to convince them to change or should I just do as they’ve always done? If I need to convince them, how would you do it?