More Cyclists get caught because more cyclists get tested, its not rocket science.
When Rugby and Football start testing the players properly, imposing upon them the same conditions as cyclists, its going to expose a lot of people and cause embarrassment. However, because of the vast sums of money involved and the damage it will do to the sport, it will never happen.
The link above includes all tests executed by USADA. That includes those tests initiated, or planned as part of USADA's U.S. Olympic, Paralympic and Pan American movements testing program as well as those tests completed by USADA at the request of other sport and antidoping federations, events, and organizations.
So, lets take a quintessentially US sport like Ice Hockey, one where you could make huge performance gains from doping or PEDs and there are just 22 out of competition tests and NO tests in competition....
As I said, cyclists get caught because they are tested.
As for le tour, its the best three weeks sport of the year...