It was this one
The thing is, it also depends on pitch conditions. If a pitch is "dry" with less cracks/grass on it, then typically a team batting can score a ton because the ball being bowled is not moving a lot. Whereas, on a pitch with grass/moisture, the ball can hit the pitch and sort of swing away or into a batsmen, making it difficult for the batsmen to hit shots and score runs. In this video, the pitch was a batting pitch, so it was almost effortless for the batsmen to score runs and hit a ton of boundaries.
And as for the stumping case, you have to realize that stumpings generally happen only when a spinner is bowling (when a bowler tosses up the ball, it bounces on the pitch, then turns away or into the batsmen) and the wicketkeeper is up, so if the batsmen steps up to hit, the ball turns and the batsmen misses, the wicketkeeper collects the ball and then swipes at the stumps (ball in his grasp in his gloves), making him out. It's a RISK for the batsmen to do that for that very reason, since he could try a shot, but get out.
As @Gouki88 thoroughly said (TP @Gouki88!), and you've probably seen in the highlight videos on youtube, but the goal of a spinner is to bowl one that starts off in the air, bounces, and then turns or makes some movement that really confuses the batsmen, or even beats him. IF there was no line on the pitch where the batsmen had to stand on or behind, then the batsmen could easily just try to take multiple steps up, and while the ball is in the air, easily just smack it out of the stadium or something while simply in the air (no spin or bounce)
By doing that, the batsmen would have a tremendous advantage. ALSO, remember that in cricket, when you try to manufacture runs, all you do is run straight toward the line next to the bowler, and then back to the line you were batting on for a 2nd run, and so on. IF a batsmen were allowed to take multiple steps and even just make small contact between bat and ball (weak contact), he's already technically halfway towards a run since he stepped up and is already halfway across the pitch, and halfway towards a run (so a very easy run). So this way with the line on the pitch, there's some risk involved for the batsmen, which makes it a little tougher for him, and also gives some advantage to the bowler in that regard (and the fielding team).
Hope all that information makes sense and sort of answers your question!