who we are going with before pulling the trigger.

If you're Avis or Enterprise etc they allow for you to attach your info so you get credit as a member of that particular company. I often look at Costco at least to compare.

I never book with a Costco, Expedia, Kayak, Orbitz. I use them all for price aggregation but always book direct from the source.

Hate buying trips through packages.

There are sometimes wild price differences on rental cars in the same city at the same time, so it's always worth looking, but I get the price and then I book at the source.

You give them your membership number, and you get all the benefits.

Also, booking through the services doesn't get you discounts that you can't get directly from the rental companies.

those rentals are spread across 5 or 6 different companies, then most people don't see any benefit from membership because they will never accumulate enough rewards to get any free rentals. I'm guessing most people either aren't aware of or forget about the ancillary benefits.

has all the answers.

Because filling out the application takes shorter than waiting in line for a single rental, and you have it for life.

Free rentals aren't the point. Saving time is. Cripes, Hertz had ads on it 30 years ago. You know, O.J. running through the airport to rent his white Ford Bronco from Hertz?