Hajj is obligatory only once in a lifetime of a Muslim. If repeated hajj curtails the chances of other Muslims who want to offer their obligatory hajj, should not people desist from such a practice?

Hajj is indeed a one-time obligatory ritual of worship. If one is afforded with a second or third chance for hajj then the second and third hajj will be counted as optional (nafl) and also earn reward for a person.

However, if it is known for sure that by offering hajj a second or third time would mar the chances of some other Muslim, then a person should abstain from this practice.