Shouldnt it be a common rule to have a timer on the speedrun videos?

Generally depends on the game - for some categories if they're really short a moderator can be happy to time it to existing rulings without use of a timer, like if a run starts on "pressing start" and ends at a certain point, all they have to do is subtract time that isn't the run if it's RTA based.

I prefer to have a timer myself because it's less work for mods imo.

The timer is required if you are using the load remover and submitting that time. Otherwise it uses the in-game timer so it isn't necessary to have the timer visible as the game tracks it and shows it at the end.

@miraclewhipes - Sorry I forgot to mention I was talking about the Demo Speedrun

ah right. like mrmcsqueezy said you can just subtract the time from the beginning and it's easy enough to get the time. it's a misc category so not many people run it anymore since the game was released. console users also can't have a timer i guess.