My newbie understanding is that there are two main reasons.
1. Completely colonized grain is fairly resistant to contamination, but uncolonized grain is a perfect medium for a bunch of other fungus and bacteria that you don't want. The less you mess with things up front, the fewer opportunities to introduce contams at the most vulnerable stages.
2. The hobby, in general, requires patience. The more frequently you check on everything, the greater the temptation to make changes when most likely everything is doing OK and just needs more time.
As a newbie, I feel like my biggest risks are that I'm not doing everything from scratch, so I'm trusting quality control to the people I buy kits and spore syringes from. Things could already be fubar before I even get started. This is why people encourage learning the tek and getting the equipment to do things from scratch. In addition, I don't have the experience to know what things should look like at all stages, so I risk annoying people by posting pictures and asking for reassurance.
I'm curious to see how the experienced folk answer your question.