Don’t look for the big, quick improvement. Seek the small improvement one day at a time.
I was recently asked to give a presentation on retrospectives at my company. After many years of doing retrospectives, it's always good to remind myself that the power and benefit isn't totally apparent to people who don't do them regularly. My wife, being a school teacher, of course laughed at me because her entire professional life is about helping people see what isn't initially obvious to them.
One approach to an elevator pitch of why retrospectives are super awesome is to look at a 1% improvement graph (shamelessly stolen from jamesclear.com):
If a person or team devotes to getting 1% better every day for a year, at the end of the year the team will be 37 times better than when they started. Conversely, if the team slides or doesn't improve or gets 1% worse every day for the same year, at the end they will be 0.03 times better... or 97% worse! This argument of course is someone hyperbolic to prove a point, however it does illuminate the need to constantly improve.
“When you improve a little each day, eventually big things occur. When you improve conditioning a little each day, eventually you have a big improvement in conditioning. Not tomorrow, not the next day, but eventually a big gain is made. Don’t look for the big, quick improvement. Seek the small improvement one day at a time. That’s the only way it happens — and when it happens, it lasts.” —John Wooden
For a more realistic calculation, if a team does a retrospective every week, and they devote themselves to being 3% better each week, at the end of a year they will have numerically improved by a factor of 4.6. 3% improvement every week is an extremely realistic goal for any team, and retrospectives are an excellent vehicle to make it a reality.