The goal is there mostly because humans like goals, but otherwise both space exploration and fusion are about the research happening *in the process.* ITER alone brings hundreds of discoveries in physics, materials, design, logistics etc each year, even though its declared goal is delayed by 5 years (but the current schedule of first plasma in 2025 is feasible).
Also as it comes to ITER specifically, it's an unique project with dozens of countries participating, and the objective being research rather than fast delivery of a working prototype. 90% of the delays in the project were specifically due to political & organisational issues rather than engineering or science.
There's a very good book I just found last year "ITER: The Giant Fusion Reactor: Bringing a Sun to Earth" by Michel Claessens, he writes about it in great detail.
