It's done in FW as a means to gate newbies into building radar to get to adv radar as well as clean up the misc tab so other buildings can be added (IE: Big Shield). It's a stopping point to reconsider radar placement. Immediately jumping to adv radar tends to hurt newbies more than it does veterans, especially when they're not aware of radar shadows. With radar->adv radar, you're forced to consider your radar placement first and you're given a "cool off" time to reconsider. A smaller QoL feature that might be more acceptable would be adding sonar to radars:
* It allows you to preview LOS gain.
* It's used in sea, so having sonar makes sense.
* LOS of basic radar is pretty low as is, so adding it won't hurt much balance wise.