Why do candle sizes have to be divisible by 24h?

there are various reasons first, due to the nature of the 24h day period second, it's a matter of consistency when we start a run it will be at a fixed time like hour candles will be on the hour, or 30mins candles on the first half/full hour as a result, in 24 hrs you are trading on the same candle we want to keep aligned with the way exchanges calculate and avoid being out of sync example if you use 7 hour candles, you will have three 7 hour candles and then one 3 hour candle, but it's displayed like the 3 hour candle has the same weight as the 7 hour candle which doesn't make sense from a calculation pov