I was looking some runs and in the tops all the people use some time of glitch like this one which makes you obtain the red card and skip all the processing area to fight with Jack earlier. This isn´t my type of run and I think that there are other people like me who don´t try because they know that they´re going to be in low places, so I´d like to know what is the reason of the absebce of a glitchless category.

There isn't a glitchless category because this game only has one glitch to use, and it only saves about 20 seconds. The glitch itself is pretty easy to pull off, but you can still do runs without doing this glitch since it's not a massive time save, and the run is a ton of fun. It would be somewhat useless to make a glitchless category just to have runs of the same caliber but only a 20ish second time difference.

To get a good knowledge on how to perform the Out Of Bound (OoB), you could watch Zeke's OoB guide or Marphoria's speedrun guide, both give great advice on how to get the glitch almost every single time (for old patches). There has yet to be a video about the new OoB with the update, but it's still pretty simple, just shooting Jack in the leg in the bathroom and then getting the dog head and racing jack to the living room