Because it is needed.
1. Proposed format.
a. Fixed arena setup with power displayed.
b. Fixed battle sequence (full auto), but battle review allowed.
c. 5 tries daily.
d. Points pegged to attack win percentage × arena power multiplier x 75% + defence win percentage x arena power multiplier x 25%.
e. No attacks in the last 5mins allowing proper calculation of rankings.
2. Reasons.
a. Instead of previewing 3 random players based on arena rank, one previews 3 random players based on arena power. This allows for a more balanced fight. Coding wise, because arena power is fixed, there will be less variation. You can use the same code as pet raids to select opponents. This shouldn't be difficult to do.
b. Fixed battle sequence allows for instant results. None of that pausing battle nonsense. I believe this also easier to program.
c. Same as before.
d. This is the formula I propose. This allows rewarding of strong players, places emphasis on attack (which requires a little bit of planning who to attack), and still rewards defence.
e. Not really necessary but the overall formula allows thw averaging of all battle results over the day.
Overall, I believe my proposal greatly reduces the impact of last minute sniping and time zones blah blah blah. Most importantly, this should be easy to code/program.
3. Future works
a. I believe given the current format, monthly rewards are rubbish. They do not reward a month of consistent play but rather a 5min investment and luck. Junk it and revert back to the daily rewards.
b. If you want monthly rewards, seriously, implement my proposal suggested half a year ago.