There's more to be said or precised about why and how Romans set limits to their own expensions and particularily in North Britain but this previous answer might interest you.

TL;DR : Rather than indigenous resistance (or lack of, rather), the abandonment of modern Scotland by Romans troops altough they did occupied it and fortified the Lowlands against native opposition was probably motivated by the cost of provincializing the poorer part of a region considered unruly enough already especially as military and political ressources would have been better used in Asia or against Dacians that inflicted a significant defeat on Romans.

As in Germania, it didn't involve giving up on indirect control, however : auxiliary troops were still garrisoned north of provincialized Britain as in Trimontium (near modern Melrose), as the limit between submitted but autonomous peoples from one hand, and free but clientelized (trough trade, subsides, military support or influence) ones was probably blur at best before the IInd century and the "materialisation" of provincial border by the Hadrian and Antonine's walls.

Hey there,

Just to let you know, your question is fine, and we're letting it stand. However, you should be aware that questions framed as 'Why didn't X do Y' relatively often don't get an answer that meets our standards (in our experience as moderators). There are a few reasons for this. Firstly, it often can be difficult to prove the counterfactual: historians know much more about what happened than what might have happened. Secondly, 'why didn't X do Y' questions are sometimes phrased in an ahistorical way. It's worth remembering that people in the past couldn't see into the future, and they generally didn't have all the information we now have about their situations; things that look obvious now didn't necessarily look that way at the time.

If you end up not getting a response after a day or two, consider asking a new question focusing instead on why what happened did happen (rather than why what didn't happen didn't happen) - this kind of question is more likely to get a response in our experience. Hope this helps!