While I agree with you to a certain extent, a big issue is that legitimate shorter distance races for masters athletes in the United States have largely disappeared.
Most masters track meets are a joke. A 50-year-old male works really hard all Spring to race a good 5,000 (sub 17:00) and he signs up for his state's USATF Masters Championships. On race day, he lines up against an age 35 male (technically a master in USATF) that is going to run 15:xx, an 80-year-old guy that is going to shuffle through it in about 32 minutes, and the lone woman distance entrant that day who can run about 24 minutes. She's in the race because the officials saw an opportunity to combine fields and go home early. Doesn't this sound like fun? Sadly, I'm not making this up as it actually happened.
OK, then move to the roads! Lots of 5K, 8K, and 10K choices out there, right? Nope! It's getting harder and harder to find much between 5K and Half Marathon these days. Races have to be longer so that entrants feel like they are getting value for their $89+ entry fee. The shorter stuff is now so geared towards fitness and fun (themed crap, Jog to Cure Something, costumes) that the actual race is a clusterf**k of walkers, costumed joggers, strollers, and dogs trying to clog the primo starting spots near the front right before the gun. The RD isn't going to enforce order because he got his money and this event is all about fun and charity. Calm down, Mr. Serious Old Runner!
I'll spare you my rant about courses lacking accurate measurement, certification, and why RDs find it necessary to add sh** like "Doom Mountain" and "Cardiac Cliff" so that the hobby jogger crowd can brag about how they slayed the toughest 5K in the Tri-State area.
Most masters just gravitate towards marathons and half marathons because those are the last events that still seem to take racing, course accuracy, and respect for real athletes seriously.