A quote is rarely final at the first attempt: the size requested changes, a line is added, a discount that was too generous comes off. Every change says something about the negotiation, but if the system simply overwrites the previous version, that story disappears without trace.
What is lost without versioning
With no record of revisions it becomes impossible to answer useful questions afterwards: how many times was this quote changed before it was sent? What differed between the first proposal and the one accepted? How long passed between revisions? Aggregated across many jobs, those facts reveal valuable patterns about the commercial process.
The number of revisions as an indicator
A quote revised many times before being sent may point to a product that is complex to configure, or to an inefficient internal process. A high number of revisions after sending, by contrast, often indicates an undecided customer or an initial price poorly judged — different signals calling for different responses, but only noticeable if the data is captured.
Balancing traceability and simplicity
There is no need to keep every keystroke: recording the significant changes — a price change, a line added or removed, a change of status — with a timestamp is enough. That level of detail is sufficient to reconstruct the history of a negotiation without burdening the system with noise.