Correction: they're not dangerous if you know how to use them.
Most people would expect to be able to safely pass the contents of $1- to any command without the contents being evaluated an extra time, because that's how most commands in mIRC work.
It only takes a very simple example to demonstrate the security risks associated with these commands when not used correctly.
vs.
If you pass anything that contains unknown parameters ($1- in an on text event for example) to /scid, /scon, /timer or /flash, then you're in for a world of trouble.
It's also very irresponsible to try and play down security risks unless you have a complete understanding yourself.