Yes, it was only special the first time a world champion was beaten in a match. So there probably was a lot of competition about being the first to achieve it.
I bet the programmers of Fritz would have liked that achievement just as much as IBM did, for example.
So I guess there was a lot of motivation to do questionable things to be the first. Any company not cheating would risk losing the race for that achievement to a company that would not shy away from outright cheating.
And why did they not put Deep Blue into some kind of IBM museum afterwards ? Why was it dismantled ? It could even have been sold later for its historical value if they wanted to.
Formula One teams don't destroy champion cars despite there being a new one every year. Some are being sold, some can be viewed in their own museums, and some are being reused at special events. There is still money left to be made with them.
But Deep Blue was much more unique that that, and they just dismantled it ? Really ?
And after all the money dumped into the project they were never interested in just proving Kasparovs accusations wrong ?
Spending millions on a PR project but not spending a few thousands to publish logs that prove it was legit ? Does that make sense to you ?
I agree with you though that a third match could not have seemed attractive to their management.
IBM retired Deep Blue because they successfully completed the mission to beat the world chess champion. The unique occasion of the machine officially surpassing humankind at chess! It's only special the first time it happens. Now everyone takes it for granted that the top chess programs would easily defeat the human champ.
IBM had no worthwhile publicity, no "buzz", to gain from a third match. And why risk losing to Kasparov? Retire while you're on top!