Not if they had more plans in the works and didn't want their "work" interrupted.
That's exactly right. If it's in their interest to claim responsibility, they will. If it's not, they won't. Simple as that.
This notion that they "always claim responsibility" is absurd on its face. Who would know if they didn't? It's impossible to know if they've claimed responsibility for every disaster they've ever caused. It amazes me that people continuously make this laughable claim.
Aside from all that, there have been other crashes where no immediate claim was made, but images from those crashes were later used in jihadi recruiting videos (AA 587 over Queens, 11/2001). Also, there was a claim of responsibility for TWA 800 (and an advance warning) that the media just didn't report until well after the fact. To this day, people still say TWA800 wasn't terrorism because the terrorists didn't claim it... a flat out lie.