The most obvious problem is the stress caused by warm temperatures and dry air inside the home. It must also be terribly embarrassing for a tree to be so lavishly adorned. Another problem is that the trees do not want to spend the rest of their lives in a container. Live Christmas trees are usually marketed at their best and with a proportionate root system. Unless they are properly maintained, they may develop circling roots in their first year.
Conifers are especially susceptible to root structure problems in containers.
The third problem is where to plant the tree when it retires. I mentioned this problem last week in association with the Canary Island pine. It is also a problem with Aleppo pines, Italian stone pines, Monterey pines and a few other miscellaneous conifers. The problems of environment within the home and embarrassment among other trees cannot easily be changed, but trees eventually recover. Proper irrigation while inside will help compensate for increased evapotranspiration.