Tanks can't search buildings either, nor can they hold land without infantry support - or, in the modern theater, air support.
Only infantry is absolutely essential to urban warfare, and to holding land.
Thing is, whoever has air superiority has the high ground and has the advantage over armor and infantry. What's more, the low logistics cost of drones is a force multiplier, for they are so much cheaper in terms of logistics, manpower, and material that it's as if there's that many more multirole aircraft to face. A force of infantry and/or armor that cannot effectively challenge the enemy's air superiority is at a serious disadvantage.
Therefore, in the modern land battlespace, one must establish air superiority *first* in order to effectively conduct offensive operations.
In fact, when one side has established air superiority and has significant ground attack capability, ground attack by the other side would not be - *ahem* - advisable.
So what, then, is the good of wasting resources on armor when it's so much *less* cost-effective than drones?