There were certainly better ways to do DRM at the time (even now) that Adobe was well within their monetary limits and interests pursuing. But of course, it was still cracked.
Also, for a hundred buck fee and some TPB/Demonoid credit, it's almost always worth it to a cracker to go after a flagship product.
There's also the running theory that Adobe was the one to release some of the cracks, namely because new releases of the Creative Suite back when it was new would be cracked nearly "instantly".
It's speculation, but the above theory would make a lot of sense - and, in my opinion, that's exactly what ended up happening, and what made Photoshop the industry leader over a pretty decent selection of alternatives at the time (though admittedly PS had already mostly established itself at the time anyway, but it could have probably been swayed).