Factors:
1) Inflation is likely impacting targets more than it is ganking ships, as small T1 ship prices are near (or sometimes marginally below) mineral cost while high-value cargos retain significant value. Combine this with readily-available PE5 and researched BPOs, and it's easy to keep costs down.
2) Tags-for-sec make it easy for anyone to indulge in periodic ganking, without having to rat for ages afterward.
3) The payout for ganking is still massively higher than for most other forms of play, aside from perhaps capital escalations in high-class WHs. Would you rather grind incursions for eight hours to get that 1b, or would you rather spend a couple hours with ten dudes looking for a couple overly-blinged mission ships or that one freighter going way over the advised limit?
4) Ganking actually scales very well with player counts; the more players or characters in on it, the cheaper the ship you need to use to achieve the gank. This lowers the threshold for action.
5) As gankers get more experienced, they're finding ways to increase their yield-- plopping down MTUs to recover their gear for reuse, salvaging all the wrecks, or doing things like reselling officer gear on the market and logging who makes the purchase for future ganking. To be honest, I'm sure it wouldn't be difficult for one player with a scanny alt in a noobcorp
I'm not sure how many of these are a product of changes, and how many were existing issues.
To be honest, my issue with the CONCORD system at present is that there's no lasting penalty. Sec status loss is an inconvenience, nothing more. Beyond that, the only deterrent to ganking is the expense threshold-- and it's clear where that's put us.
Ideas:
1) Increased sec status loss, and decreased sec status cap. Be forewarned: random, nonsensical numbers ahead. So-- instead of marginal sec status losses when ganking, increase the up-front sec status loss markedly, and also marginally decrease a character's max sec status-- so someone who is at 0.0 to start may pop straight to -1 on a gank, and have their max sec status drop to 4.5 or some such-- and on down, so that even as a character repairs their sec status to get back into HS to gank, their cap continues to lower, until eventually they start capping out of highsec. Consider this a game equivalent of 'three strikes' laws, resulting in lasting, long-term penalties. Right now, there are none.
2) Impounded goods. What if wrecks/loot involved in a gank were impounded by CONCORD? Both parties lose the goods, then. There's still significant damage in ganking, but it can't be done for profit.
3) CONCORD pods. This would shift the focus back onto gank alts, instead of weekend gank trips by mains-- but it might still combat it to some degree.
4) NPC corps can't go safety red. Could you imagine the howls?
5) Corporations get a security status rating, and a poorly-rated corporation starts seeing CONCORD effects in high security space.
To be honest, I don't think 2) is a workable idea. 1), 4), and 5) would be frickin' hilarious, though -- especially if each player in a corp gets a derived sec status hit when their corp gets a hit.