This picture speaks volumes, so visually take it in. Standing up in someone’s Guard should be a priority. It gives you the assistance of using gravity to help with the technique performance.
Operationally, the act of standing in Guard provides separation between the two bodies, making the job of breaking open the Guard so much more effective than doing it only from the knees. Yes, it can be difficult to do at times, but by putting in the reps it does get better.
The number one reason students don’t stand up is fear of getting swept, or because they don’t understand how to properly do it. My advice, FAIL FAST, and keep working on it. If at first you don’t succeed, keep trying, and learn from your mistakes. As you get more comfortable with the movements, you begin understanding that there is a process to do it correctly.
Lastly, getting better at opening Guard from standing establishes progression. This can be very important during an even match where forward movement can be the difference between winning and losing.
Learn. Drill. Roll. TRANSFORM!