There is no reason for not using LN for small transactions up to $100 or so, which make up to about 25% of current BTC on-chain transactions.
How did you come to the number of 25% ?
I believe way more transactions are effectively sending less than 100$.
It's a rough estimation based on the observation that the median transaction value is about $400 at this moment. See
this graph. This is however a relatively high value compared with the last 6 months, at some days the median was even below $100, in this cases you're right.
LN is a niche for people who spam(spend more than once a day)
by the time someone gets paid. works out how much they want to deposit into LN for spending habits of the month.
I am currently not using LN regularly (besides from a little testing), but even now - when we're far from the frenzy at the end of 2017 - between Monday to Friday I often refrain from spending on-chain BTC even if I wanted, because of the high fees.
So no, it's not only for "spammers". I think LN is useful for everybody who wants to move funds of a value of less than $100 more than once per week.
It definitively has drawbacks like the "have to be online problem", that's why I'm still not regularly using it (other simple reason is that almost no BTC-accepting service I'm using accepts LN, but I may search for alternatives).