if I do not have a LN channel open, I could pay $2 to open one, pay via a LN invoice, and pay for many other things over time, each costing a small fraction of a penny.
because not all counter parties are guaranteed to b funded or online to make payments for you. you will find you will need to open more than one channel to have a reliable service. so opening costs would be more than $2
also you would have to close the channels eventually.
on average most open 5 channels. so thats $10 upfront with maybe $5 when closing. so thats $15 of fee's just to use LN
now how many transactions in say an average month(average preplan spending habits) do you think you will make
30=average cost $1 60=average cost $0.50 120=average cost $0.25 6000=half(fraction) of a penny
LN is not a solution for everyone as not everyone makes transactions often
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IOU's can be signed too.. just not settled.
imagine bank cheques untill the cheque is cleared a signed cheque is just an IOU
old bank notes, with signatures from important fed guys are IOU's 'i promise to pay the bearer the sum of..'
credit/mortgage agreements are IOU's
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as for the whole 2 party sign transaction stuff. seems your reading old 2016 documents about LN. read up about factories, and htlc's. these dont get broadcast.
also realise LN payments themselves are not locked into blocks and community vetted. they are just agreements between 2 parties. we already have cases where parties are opening channels using collateral thats not even bitcoin. but where others if they seen the msat balance would think it was.
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but getting to the topics point. LN is not a bitcoin network. it is not a feature solely for bitcoin. it actually requires people to drop using bitcoin and use this other network. thus does nothing to scale/adopt bitcoin, but instead to make other networks of commercial gain more attractive
yet people forget the whole fundemental reason for bitcoin
a. independant self control of funding/wealth
b. pay anyone anywhere without barrier
c. no trust required
now lets look at LN
a. requires a counterparty, infact teams of counterparties for routing, all signing get your payment to destination
b. counterparties/routers not online 24/7=barrier.
c counterparty risk they can edit their node to do something unexpected, no guarantee of settlement