In the historics of ATC, the SIDs Standard Instrument Departures were initially published as "loss of communication procedure" and, in practice, it was somewhat rare, particularly in the USA, to navigate a SID. Once ATC gives you a vector, they give you a new clearance, it cancels your SID clearance, unless they clear you back to the SID...
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One thing I always did, was to program the "exit point" of the SID as the INS waypoint 9 (the last one on old C-IVs) as I expected departure to initially give us vectors/climbs then eventually "direct to" that point...
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A few years later, came the STARs arrival routes... same story. So in all practicalities, SIDs and STARs were only flown in case of loss of communications. I remember often being cleared from JFK (when passing FL230) "direct to" HECTOR , the initial STAR entry for LAX arrival profile descent.
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Then I noticed that Europeans got into the SIDs/STARs, and found it quite convenient to issue the full SID/STAR profile, less work for them. No vectors, no climbs or descents bla bla... just go as published, and let us sip our tea, don't bother us. London became notorious for that, with my PanAm soul, (and opinion)... soon followed by Frankfurt, them Paris and Amsterdam. Complicated zig-zags. So in Europe, they sit on their hands... In the USA, they still expediate with vectors.
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Loss of communications if often NOT A LOSS of communications. It is ATCO that gives you an erroneous frequency change, or you, not copying the correct frequency to dial with your fat fingers twisting knobs. Thanks God for the A/B switch on your VHF COMM to get back to your previous frequency to say a "CONFIRM 123.4...?"... With the old radios, I recall "loss of comm" and unable to recall what the previous one was - and going on 121.5 with my tail between my hind legs to query "who to speak to now"...
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Been there, done that... you guys will too.
Arf, has my dog says...
Happy contrails