Actually I do not remember any official statement about this. But this is just policy. Itch does not make official statements about most things. This is public community. While leafo sometimes posts here and even sometimes makes announcements, a thing like stating reasons for anything, is rather rare. Maybe for something concrete, like size limitations. But for features or lack thereof, no.
So all this is community speculations and discussion. But try to deduce from these three facts:
Single tag exclusion was developed by leafo in less than a day some six years ago.
The feature was not removed since then.
But not expanded upon either.
My deductions are, that single exclusion was super easy, and multiple exclusion is too much of a hassle to implement compared to the demand. They have server statistics, they know how often single tag exclusion is used.
And more imporantly, they know how many people used the feedback button to suggest features. The very first topic of the feedback button drop down box is feature request.
