Hart, who is hoping to represent England at the World Cup next year, was replaced by Adrian in goal for West Ham's game against Manchester City last weekend as he was not eligible for the game as he is still under contract at City.
The England global moved to East London on the premise he would be a regular starter to cement his place as the Three Lions first choice keeper ahead of next summer's World Cup.
"I always have compassion for the players as well, that's why it wasn't an easy decision on Joe", Moyes told reporters.
However, Moyes suggested West Ham's survival came before the goalkeeper's ambitions.
West Ham 1-0 Chelsea. "We've been in good form recently which is why it's so disappointing".
"Joe wasn't happy, I told him the reason why and that happens at clubs all over the country, it's a manager's job".
Speaking to TalkSPORT, Pearce said: "He [Hart] is disappointed that he hasn't been playing".
And Hart's inactivity under Hammer boss Moyes leaves the 30-year-old's place in serious jeopardy.
West Ham are aiming to move out of the relegation zone on Wednesday when they host Arsenal at the London Stadium.
Chelsea have it all to do to try and get themselves back into the title race.
Huddersfield Town will be at home once again this weekend as they take on Chelsea.
I think when you play every three days, it is impossible to have a training session and to work on the physical aspects.
Five of the visitors' nine league away goals so far arrived in a single match against an Everton team in poor form under the doomed Ronald Koeman, while they have failed to strike a couple of times in any of their other seven games on the road.
"Joe is incredibly experienced".
"We just didn't play our stuff".