Imagine the queues in the shops if Visa batched their transactions up and authorised your payments in 10 mins blocks. That is probably the main reason Btc hasn't (and probably wont) taken off. People just don't want to wait. Even if they halved it and halved it again, that would still be 2.5 mins waiting for payment to clear. The lightning Network is ok but if your main selling point is something that just bypasses the main protocol, then why bother with the main protocol.
Probably, Litecoin has a 2.5 mins block time but it didn't take off though. They have the option to use that if they feel Bitcoin is slow for them. I'm not encouraging people to use Litecoin because of what I said, invest at your own risk. For now it's not necessary to speed up the block times because the network would always be empty.
What's not to like about the Lightning Network it's like squeezing multiple transaction in to one.