I hate those stupid calculators. They are very misleading. And here’s why:
Part of the value of a hand is the size of the pot that you win when you win, and how much money you lose when you lose. A hand like 10-8 will make a greater percentage of ‘wins’ with top pair, and 98 will make a greater percentage by making straights. When you make a straight in holdem, you generally win much more money than when you make a pair, because you can make money from people with hands like top pair, two pair, trips, and smaller straights. If you have the best hand with a pair of tens, the only action you are going to get is generally action you don’t want (people with two overcards, or drawing to straights and flushes).
From that standpoint, 98 is a better hand than T8, all else being equal.
Note that as you go up in rank, this starts to change, because the chance of your top pair standing up is greater. So AQ is better than KQ.
Also, as the number of players in the hand goes down, the value of bigger cards goes up, and the value of connectedness and suitedness goes down.
This is why using hand calculators is a bad idea. It’s much better to learn the theory behind the game and understand why hands are good and bad, rather than just memorizing a bunch of win/loss statistics that are mostly useless. Players that have an intuitive understanding of how strong their hand is for every situation will do much better than those who play a more ‘static’ game.