Another part of mbr's bringing their own med's to BMQ...they may use them to 'get thru' an illness or injury (whether it be a cold, or an injured ankle or something) that may get worse (so they *take more*, or make the injury more severe).
Let's use an example where they, say, roll their ankle over. Not wanting to be the *MIR Commando*, they dip into their Ibuprofen stash, thinking they'll just soldier on thru. Over the course of a few days, or a week, or more..the actual injury worsens, to the point where they DO go to Sick Parade, and the MIR staff find out it is now a moderately severe injury, and the mbr now gets put on PAT for a 'condition' that might have been dealt with effectively before by 2 days light duties which lead into a weekend off, where the condition may have corrected itself, and the mbr would not have been required into a ST (Suspended Training) scenario.
Sure, its just an example, but one I've seen happen a few times, and not in the mbr's favour where, at a crucial time, say before the field portion where the injury was then serious enough that the staff noticed it, ordered the mbr to MIR, and the mbr was properly assessed and documented with injury X. Unfortunately, it was immediately preceding the field portion of the course, which was a requirement to pass the course, and you could not complete without medical restrictions/MELs. Mbr was RTU'd off the crse.
While trying to 'soldier thru' is a good thing, most candidates attending BMQ/IAP do not know the difference between what we used to deem *hurt* and *hurting*. Hurting was expected, and accepted. Hurt was "go to the Doc". An experienced soldier knows his/her own body, and knows the difference between the 2. Recruits..not so much IMO. I had a QL3 candidate in 2001 come hobbling down the stairs from the 2nd floor...not knowing I was standing there. I ordered her to the MIR. Turned out she had a torn ligament in her knee or something to that effect...caught early enough that it didn't stop her from completing the training, including the mandatory 7 day defensive ex. The 2 weeks with PT/drill restrictions that were allowable under the CTP/CTS made the difference.
Also...if you don't go to the MIR...it will never be documented in the first place that you were injured. In my case for the one that counted (back injury), the fact that I had proper documentation made my dealings with VAC almost painless....almost.