Thanks for the question @ActionTux
Yes, I am a US-based pilot. Over here, we can request in the flight plan whatever we want. The route ATC actually clears and assigns is a completely different matter.
Once upon a time in the US, following airways was critical because of radio-based navigation. The routes were defined by omnidirectional beacons (NDB) and then more routes were added through the rise of VORs. Following a route made life easy for the pilot to navigate (fly OBK 270 radial outbound for 30 mi and then switch to DPA inbound) and easy for the controller (J244 traffic 5 mi in trail, both at 250 kts, 16000 ft).
We used to have big wall charts of IFR routes in order to figure out cross country routing.
When SatNav became dominant (GPS, GLONASS etc), the routes no longer needed to follow low or high airways as navigation became markedly easier. Additional GPS-defined waypoints began to pop up and color the map. Then RNAV based GPS routes (Q-routes) showed up.
ATC needs to deconflict and manage the flow of traffic around the country. So while we now have a blend of old style routing and point to point routing, the FAA publishes several different routing mechanisms:
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coded routing: primarily intended for turbine engine/Jet and airline use 15 years ago. You punch in to the FMS a string of characters. As bad weather befell an area, these are a predefined playback of alternative routings. Imagine you’re in queue for departure and weather is moving in. ATC is now offering reroutes around severe turb. Rather than typing in “KEWR NEWEL J60 DANNR RAV J64 BURNI TYROO QUARM AIR HVQ BULEY J91 ATL YUESS Q79 MOLIE WLACE4 KPBI” while in queue for the runway, ATC simply gives you EWRPBI64, which contains all the above routing. I don’t think coded departures are used as frequently as they once were due to the significant fuel reserves required. Routing can sometimes be 50% longer. If you’re going to accept coded routing, you better have full tanks.
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TEC Routing: Tower Enroute Control - low level routing from Approach to Approach and ATC towers along the way. Rather than transition to the enroute Center control and be log jammed at times from packed airspace. These routes can be found in the Charts Supplement Publication (formerly known as the AFD Airport/Facility Directory).
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ATC Preferred Routing there is a listing of origins and destinations along with government preferred routing. These routes can be found in the Charts Supplement Publication.
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Recently assigned I think this is what most GA pilots select. Modern tools allow the pilot to select a predefined routing based on what ATC reports back to major navigation institutions as having recently been cleared and categorized by airframe.
Today, although a lot of navigation happens primarily through GPS, much navigation still happens through radio based. As a result, pilots are now able to request routes appropriate to the equipment they are flying with.
A lot of information there, but the long story short is that we stuck to routes once upon a time but today have more freedom to go waypoint by waypoint.