Late to the party, but could not agree more. As a person who has spent over a decade working in large corporate it is absolutely asinine to me that they would not make it accessible to us unless it's for the reason you are mentioning.

A unique transaction ID is the corner stone of data in the database as well as in doing any kind of quality analysis en mass. Removing a feature of this nature (and yes, the prior poster is correct, you would have had to intentionally exclude it, there is absolutely no way it isn't there in the background and could be added with almost no effort) would make me advise any company with enough size to require quality custom analytics choose a product other than Quickbooks.

EDIT: This thread is around for a 4th year now and all that Quickbooks seems to have to say is "submit a feedback." This is not about some niche request a small number of people wants. As many people have indicated if you are an accountant that is half competent you'd consider this an absolute must for many reasons and combined with the fact that it should be an easy feature to implement the only logical conclusion is that Quickbooks doesn't think it's in their best financial interest to add it. If that's the case then just be honest.