I'm hoping that wasn't sarcasm!
I'm not familiar with Kompakt, so I don't know whether it lets you select a specific MIDI input port for each virtual instrument, but DAWs let you select a specific port for each MIDI track.
However, one thing DAWs usually do which can be problematic is to default a MIDI track's input source to "all MIDI devices" and "all channels," such that the data from all active MIDI inputs are merged together. In that case it will definitely be a problem that all three keyboards are transmitting on the same channel. I suspect that this "listen to all ports and channels" default behavior is done to make it easier for beginners to set things up without having to understand about MIDI ports and MIDI channels: "Just connect your keyboard to your computer, add a MIDI track to your project, and away you go!"
But DAWs let you change the input source for each MIDI track to a specific device (or port), as well as to a specific channel. Hopefully, any virtual instrument host program that lets you control multiple virtual instruments at the same time will also let you select a given input port and/or channel for each virtual instrument.
It's not that uncommon for inexpensive keyboards and controllers to be "locked in" on their MIDI channels. I have four Yamaha PSR-E/YPT models like that-- the various parts (Main, Dual, and Split, as well as the accompaniment parts) are transmitted on specific channels and there are no functions for assigning them to different channels.