For the challenge. Donkey Kong is one of those games, that I would argue, is not like riding a bike. If you're not playing regularly, skill level dissolves pretty quickly.
I play a variety of games - a lot of different iterations of street fighters, racers, any number of console games. Street Fighters I can walk away from for months at a time, and within a couple hours be back to 90-95% of peak performance. Racers, the same thing. Heck, I gave Madden 99 on N64 a try, a couple weeks ago, which I used to play daily with friends back in...well, '99...but havent' touched in almost 20 years. The mechanics came back pretty quickly, and by the second game against the computer, I dominated.
Donkey Kong, however, not so much. I haven't focused on it in a couple months, sat down committed to having a solid run last weekend, and came up just shy of 300K.
If I played every day for the next 2 weeks, I could probably scratch out a 700k+ game eventually...probably. Days/weeks vs. hours. It's both challenging and infuriating at the same time.
Maybe it's different for the 1M, 1.1M, 1.2M players.