Since most tips would probably be between 10 and 1000 satoshis, not exactly life-changing amounts, I think its a win/win either way, whether you go with 3rd party service or not.
While the idea would indeed give a boost to LN, I don't think that making a LN channel for 10-1000 satoshi would worth the hassle.
And if somebody wants to send more meaningful tips, a lot of users have a tipping address in their profile. And it's rarely used.
Yes, making it easier would increase the usage, but I don't expect wonders. And Theymos' option to
not hold users' money is a pretty healthy one.