But why should participation in a national cup have any bearing on ambitions in the league? I don't think it's unusual to enter two - in England for example a large amount of non-league clubs enter the FA Cup and also the FA Trophy or the FA Vase, depending on their level.
Almost the entirety of the Highland League has no interest in being part of the SPFL. They're only there as a feeder by accident of history and geography. It wasn't something they asked for as such, though they did get what they want - a closed shop with no way out the bottom despite interest from Banks O' Dee.
As far as I know, there are no current members of the South of Scotland League interested in promotion to the Lowland League. In the East of Scotland League there is a lack of clubs interested /able - Kelty will change this. Any Junior club committing to the pyramid has to join the EOS or the SOS - like kelty have. For the clubs in the West this is a massive backwards step - would you like to see your club play in the Fife Juniors? That's the kind of step down that it is. The SJFA are also a vindictive organisation and if a Junior club decided to leave the LL, they would have to rejoin the Junior world at the bottom - in the west that would mean a 4 division relegation and 3 promotions to get back to the top level - that could mean oblivion. Until the pathways are more fairly marked, and until a decent alternative exists in the West, Junior clubs would be wise to consider the ramifications of moving onwards.
Why we even have Junior / Amateur / Welfare FAs says so much about the poor governance of the game outwith the national leagues. All for one and each association for itself. As I understand it, the Junior FAs came about because of a lack of help for smaller clubs from the Senior one, the Amateur FA as a result of the SJFA accepting professionalism and the Welfare FA is a historical anachronysm whose ongoing existence baffles me.