On the size issue, people mistakenly think being allowed to take a bag on many times means it's legal size. That is plain wrong - many roll-aboards actually exceed written airline limits (which vary among carriers). I bet they've defined Bogota as a place where carry-ons limits have been abused to an extreme.

Plus, the dogs at IAH can sniff the checked luggage.

They can also enforce carry-on weight limits (40lbs).