Ludlow never expresses exposure to welsh danger in its petitions, unlike Shrewsbury (constantly) and Hereford (occasionally) although similarly placed. Ludlow regularly got, often long terms of, murage (Coulson). Coulson goes on to suggest that the influence of the powerful lords of Ludlow castle and town may be a reason why such special pleading was not required at Ludlow.
Clearly the influence of local magnates is important but I suspect some of the reason for the repeated expression of danger at Shrewsbury is due to clerks coping out the previous petition rather than to conscious perceived need to appease royal concerns. (Copying a previous example reduces composition errors. This was more important in the days of quill and parchment because error correction was more difficult and the costs of parchment were so high. There may also have been reduced legal cost.)