I ran into the same thing when I replaced my windows.
They want both of you there, then offer you a "special" discount if you commit at the time of the appointment (as if they wouldn't still do it if you called them on the phone the next day).
I think they also hope they can figure out which of you is making the decision and which buttons to push to make it happen now rather than later.
We had two companies come, and both pissed both of us off. I'm glad they did. I went to a home store (not Lowes or HD who have their own installers) and found the replacement windows kits. They even had a guy come out and measure to double-check my measurements (30 miles away). The kits were pretty easy to install - I just had to be careful pulling off the trim around the old windows so I could reuse it. We saved a boat load of money and ended up with much nicer windows than we were willing to pay for with the installation company's price sheet.
You can also know it was done right if you do it. We moved 4 years later and there are all kinds of drafts around the double pane upgrades that the previous owner of our new house had installed. I guess they decided putting the insulation around the new window guides was an unreasonable burden. Kind of defeats the purpose of the double panes.
All I can say is be careful who you choose to do this work if you don't do it yourself. Get them to explain exactly how the surrounds fit in the window casings and what insulation is used. Ask them about a warranty or something in writing to resolve any drafts you might experience over the next year.
The Atlanta area has been such a housing boom area for so long, that even in these hard times, companies are still cutting corners and I'm pretty sour on the whole industry. Hopefully, contractors in your area aren't that bad!
PS - you might also check out and join Angie's List if there is one in your area. They have definitely saved us plenty!