Wouldn't in game time be more fair. example: two speedrunners run a game. one has a trash computer, and one has a godlike computer they both take the exact same route in a run, their in game time are the exact same but due to the run being timed in real time not In game time the on with the better computer wins. I think this is unfair this because this dosen't put everyone on the same playing feild.

Because it is a lot harder to time in IGT, unless there is an in-game timer that does not track loads.

If the in-game timer is not used in the run, that often means that the timer can be manipulated in some way that creates an inaccuracy in full game runs (which can include excessive pauses), or, there is gameplay at some point during the run that is not tracked with the timer. I would suggest consulting with the game's moderators to find out the specific reasons for not tracking igt.

Most games don't have access to an in-game timer. Then building an autosplitter to get to the in-game time is not something everyone can set up. Also not all the runners are able to run with an autosplitter-enabled timer. So yeah... as you can see, lots of different things that don't make it possible in general terms. For the games where IGT works it's cool that it works.

The first obvious reason is that not every game has an In Game Timer. The other one is sometimes IGT is not very precise, since things like hitting continue after you die may mess with IGT and make things unfair.

Also not all speedruns are on a computer, obviously console or mobile runs can have lag or slower loads but (to my knowledge) it's not as much of a problem

Aside from all the reasons mentioned above, I'll also add that sometimes in-game timers are somehow tied to FPS, leading to some ridiculous comparisons between PAL/NTSC versions or even between same versions on different hardware when playing on PC, so they aren't 100% reliable.

sometimes the in game timers are broken or they dont actually reflect the time of your run. Its not that common but it can happen

In an ideal future, Visual Autosplitters will be perfect and we can have loadless times on every game easily

Because IGT isn't necessarily consistent, rarely has good accuracy besides racing games, some don't include menus, some include loads, some actually can just straight up overflow / underflow / bug out, weird rare cases of IGT not going at the same speed depending on configuration and potential for manipulation The pause buffer abuse issue is also a concern though somewhat lesser

Some more recent games using disguised load screen in gameplay will also still cause the runs to give an unfair advantage to people with fast loads.

LRT > IGT all day. Its only problem is accessibility to console runners