I feel this is partly due to the 1-to-1 selling style of most insurance salespeople... it moves like molasses in a digital world.
Another issue is the wholesale price. You need to be selling a lot of a particular type of insurance to get the best pricing for your clients.
Having the market to place insurance is important. Many small commercial insurance brokerages end up having to send things to a "General Agent" who has more markets then you do but marks up the policy higher so now you are not as competitive.
Advertising is tough, very competitive. Especially now with all of these funded to the hundreds-of-millions companies like eBroker and others coming on board.
I went from sending about $18-$22 per click for commercial insurance keywords on Google Adwords 3 years ago to upwards of $28-$35 per click now.