Sometimes practicality isn't the point of research. A Mars colony isn't about being a better place to live than earth. Moreso, what can we learn about living on Mars that would make life on earth easier. Further, if we ever get to a point where terraforming Mars is even viable on a generational scale you have an ecosystem that you can afford to experiment on instead of damaging your home planet. There's also the point about make humans multi planetary which makes us much more resilient to basically any kind of extinction event.

I really don't think anyone has ever made the point that colonizing Mars will be easy.