England surrendered a 2-1 half-time lead at Wembley on Saturday after Lamine Yamal had opened the scoring. Anthony Gordon and Harry Kane turned the match around, but Spain responded through Alex Baena and Mikel Oyarzabal to claim victory.
Palmer was absent after withdrawing from Tuchel's squad because of an injury, despite initially being recalled following a strong start to the season with Chelsea.
Tuchel said Palmer was missing "too many opportunities" to impress him at international level.
The 24-year-old has made only three appearances for England since Tuchel became manager and has repeatedly been affected by fitness problems.
"He misses too many opportunities," Tuchel said. "I don't blame him for it. It's just the fact."
The England boss stressed that being present in camp is important because it gives players an opportunity to demonstrate their qualities directly to him.
"I only want to rely on what I personally witness and see within my team," Tuchel said. "For that, you have to be in camp."
Palmer was also left out of Tuchel's World Cup squad after struggling with injuries, making his latest withdrawal another setback in his efforts to establish himself under the manager.
Palmer had played the full 90 minutes for Chelsea against Brentford before the international break, prompting questions over whether his workload was being managed.
Tuchel rejected that suggestion, saying Palmer had been playing with pain and discomfort and could not perform at his highest level.
Chelsea subsequently informed England of the situation.
Palmer has experienced several fitness setbacks since Tuchel took charge. He withdrew from an England camp in 2025, missed several further selections and later returned to feature against Uruguay and Japan.
His latest absence means another opportunity to work with Tuchel has been missed.
England must now focus on their next Nations League fixture against Czechia in Prague on Tuesday.
Czechia also lost their opening match, going down 2-1 to Croatia, while England will need a positive result after their defeat by Spain.
Tuchel has other attacking options available, including Jude Bellingham, Morgan Rogers, Morgan Gibbs-White and Eberechi Eze.
For Palmer, the priority is now to recover from his latest injury and return to full fitness.
His repeated absences have not automatically been treated by Tuchel as evidence of a lack of commitment, but the England manager has made clear that regular availability will be important if Palmer is to strengthen his position within the national team.
With England facing Czechia, Croatia and another Czechia fixture in quick succession, Tuchel will have to continue building his side without one of Chelsea's most influential attacking players.