Never mind data showing the insignificance of stadiums. The projects become government-sponsored monopolies toward which consumers dollars are steered. In the case of most new stadiums, local taxpayers pick up part of the cost whether or not they attend games, and even if they loathe the pro sports monopolies. In many cases, long-time homesteaders are forced to flee their deteriorating neighborhoods, selling at a loss. The bureaucrats and nonprofits behind this process then vilify private landlords as greedy, unscrupulous, etc.
New projects require that old projects be destroyed.
Existing stadiums and houses are a threat to developers since they might be pressed into use, thus presenting actual competition to new plans. Seattle demolished the Skydome as a condition of construction of a new stadium. Were it still around, it is possible a minor league baseball team would outdraw the Twins. Supposedly, money would be saved by hosting a new hockey team in the same building as the NBA's Minnesota Timberwolves. But once government gets involved, saving money becomes antithetical.