Most likely because a 'holy war' against the Moors was already happening (the start of the Reconquista arguably predates the First Crusade by 300+ years) — an explicit papal call to arms wasn't all that necessary because the Spanish kingdoms were actively fighting extended wars to reclaim the Iberian peninsula.

There was plenty of support and sanction from Rome for the Reconquista, which rapidly took on a religious character — initially, they were geopolitical wars between neighbouring kingdoms for control of territory, rather than being immediately conceptualised as Christendom vs Islam, but that understanding arrived quite quickly.

There's a growing school of historiography which interprets the Reconquista as part of the wider 'Crusader era'. Here's a Ph.D thesis by Miguel Dolan Gomez I found, which addresses quite effectively the religious nature of the Reconquista, and argues quite convincingly that there was a distinct transition point — the Battle of Las Navas de Tolosa in 1212 — after which the Iberian wars took on the character of the crusades.

I think this section provides some useful context for your question:

The military and territorial struggles between the Christian north of Spain and the Islamic south were associated with the crusades to the Holy Land from the beginning of the First Crusade. By the time of the Second Crusade (1147-1149), the papacy came to view combat against Islam in Spain as part of a larger struggle between the Christendom and the Islamic World. International participation in Spanish military campaigns, which began as early as the mid-eleventh century, grew with the extension of crusading privileges and rewards to the Iberian Peninsula. Yet in the twelfth century, crusading remained firmly focused on the Holy Land. Popular enthusiasm for, and conceptions of the crusades were thoroughly shaped by the triumphant capture of Jerusalem in 1099 and the defensive needs of the Latin East.

The Vatican treated those fighting the Reconquista much the same as they treated Crusaders, particularly with regards to the indulgences they were granted. But Reconquista can be seen as a second front in the Christianity-Islam wars — the Crusades were always focused primarily on gaining and retaining Christian control over the Holy Land — which I suspect is why it has not traditionally been classified as 'part of the Crusades'.

Isn't the reconquista exactly what you are talking about?