There are reasons why IndyCar races on so many street circuits. That’s where the fans are and the race promoters are dependent on ticket sales to make their money. Unlike F1 where almost all of the races are dependent on state-sponsorship, most IndyCar races don’t have the taxpayers footing the costs of having the race.
Additionally, as I recall there is a limit on the number of top-level motorsport events an F1 circuit can hold. Montreal had until this year the NASCAR and the Grand-Am Series. The series already spends a large amount of it’s money paying the teams to participate in the Sao Paulo race, going to Interlagos would be more expensive. COTA is being looked at although it seems COTA is using it’s other race weekends for V8 Supercars and ALMS. As for the Indianapolis road course, really? This recent article pretty clearly details the reasons why IndyCar shouldn’t be going there.
I also think that IndyCar is trying to avoid F1 tracks so that we can’t directly compare laptimes. This is because while the and IndyCar has relatively similar downforce and power to a modern F1 car (obviously with the continual refinement of F1 the downforce is higher and as for power it depends on the turbo boost level but if the engines were turned to full boost design limit then they would crank out about 900+ bhp) the stronger, and thus heavier chassis required for ovals slows the cars down. This is easy for a casual fan to notice, but difficult for them to understand.