You're completely right, people are lazy, but online dating is also way more work than it has to be.
Women receive so many messages that it becomes overwhelming and too much work and men try sending earnest messages for a little while and then concede that it's basically a numbers game. These two phenomena are self-reinforcing. The more messages women receive, the less likely they are to respond. The more messages a man doesn't get a response to the more likely they are to put less effort into their messages. If you solve this problem, you effectively solve attrition rate in dating sites.
If you look at an old inbox full of sent of received messages for a man versus a women, you'll notice something interesting. The woman's inbox will be full of avatars next to almost all the messages. Men don't delete or suspend accounts. Now if you look at the inbox of the men on the other hand you'll notice that more and more of the messages have the default avatar next to the name as you move back in time in the inbox. This is because many women become totally overwhelmed by the number of messages, the quantity of them that are vulgar, etc.
I've talked to a bunch of people about this (because I'm one of those few people that has no problem talking about online dating because like you I think it is the future) and the conclusion I've come to that many people agree with is that online dating needs the equivalent of the spam button in many email inboxes. However instead of saying the words "Mark as spam", there should be two buttons, one that says "Mark as did not read my profile" and one that says "Flag as vulgar or offensive". The first button is to be used every time a women (or a man) receives a message where someone sends a one line message with no content specific to the recipient or any message which is obviously cookie cutter (cut & paste job)[0] and the second should be used whenever the sender is overtly sexual or mean.
Every time these buttons are used it should impact a score on both the sender and the recipient. For the sender, they're "doesn't read profiles" score should go up and for the recipient that used the button, their "cares that senders don't read and consider their profile" score should go up. The same goes for vulgarity/offensive content. The balance of these two numbers should determine if the message makes it through to the recipients email inboxes at all in the future. You could even warn senders when their score starts getting too bad, like "This message will not be delivered to this user because you've been flagged as someone who doesn't consider the content of user's profiles when crafting a message" or "This user only receives messages from people who take time to craft a personal message". If the sender then goes back and significantly modifies their message before sending again (verified via a text diff and possibly the passage of time), then send it through. This time however, if that message gets flagged by the recipient, then it counts very negatively towards their score.
If you use an approach like this you should be able to keep the inboxes of females (and desirable males) with a high signal to noise ratio. This will greatly improve their experience and lead them to respond to more messages and not get so fed up with the bullshit messages that they either quit responding or quit the site entirely.
[0] The only counterpoint to this are messages that achieve the Forer Effect[1]. One of my friends has crafted some particularly generic messages (his own admission) that presses all the right buttons just like horoscopes texts do and he gets a pretty solid response rate despite the fact that those messages are just cut and pasted. He's even frustrated that his well thought out personal messages often perform worse than his generic ones that play to a recipients own positive self image. TBH, I'd like to take Forer's original text, and modify it for OkCupid to see how it performs. Besides crafting the message, I'd need to figure out how to produce an acceptably generic profile that still conveys enough authority for the recipient to think the fake profile has the authority to make those statements/judgements.
[1] http://en.wikipedia.org/wiki/Forer_effect