An interesting discussion everyone.
A few quick and easy answers...
Low numbers of the early issues? Smaller print runs and some were shipped to the USA for early attempts at US distribution - where they promptly disappeared.
Of course, people have also had longer to buy those back issues now, so it's logical that the early one will run out first as well. An example - only a couple of heavily damaged #7s left now.
No, reprinting old copies is NOT an option. The computer files don't exist, the advertisers won't pay again, the number required is much smaller than a normal print run.
What IS possible is that some of the featured bikes in the early issues being revisited sometime in the future, either in a recap magazine or book format, like Ray's book, Motocross Racers.
As for the mix of bikes in the current issues, it's always like balancing on a tightrope when there are so many different interests in the one sport and period. We try to achieve a reasonable balance of old and new, but there will be some issues that have more of one era that another, just due to the bikes that are available for that particular issue.
The good news is that there is an enormous amount of stuff still out there to cover, so we won't be running out of stories anytime soon!