It could be that they, like many other people, are not aware of alliances and partnerships that allow concentrating miles and points. Many people may think that they are going on a business trip on an airline that they will never use again (or not use enough to collect mileage for an award or status), so they don't bother with collecting the miles or points. They may become more interested if you tell them about airline alliances and partnerships that allow concentrating the miles and points so that they have a good chance of getting an award or status.

For example, I have flown or will fly in the near future nine different airlines, but seven of them combine into two frequent flyer programs, both of which have yielded awards that I would not have gotten otherwise (I also got an award on one of the other two).

Sometimes, mere membership in a frequent flyer program can be useful, even without status. Holding a Southwest Rapid Rewards card when flying Southwest out of PDX lets you use the "elite" security line.

Also, a lot of people are not aware of hotel loyalty programs that can be useful even if you don't stay there enough to get awards or status at the hotel. I got a free breakfast coupon at a Hilton once just for having a Hilton HHonors account with zero points in it (those without HHonors accounts did not get the coupon).