But based on my observation, the low fee and fast transaction does not contribute too much to the adoption. Adoption rate always rise when the exchange rate rises (In a fiat money flooded world, no one really need bitcoin to buy groceries, majority of people treat it as investment/speculation, rest are money launderers, drug dealers and gamblers...)
In fact, the exchange rate risk is magnitudes higher than the fee, so spending 0.0001 bitcoin or 0.01 bitcoin for fee really does not make any difference since the biggest cost comes from exchange rate risk
This is one of the main reasons I believe that pushing for a block size limit increase with the hopes that bitcoin adoption will grow and will have to be contained in the blockchain is faulty rasoning. That in addition to the fact that most adoption bitcoin has had up until now was thanks to some kind third party technologies that made it more accessible, usefull, or somehow appealing to use. To say that a lightning network or any third party technology to support innovation and more transactions per second on top of the existing technology would be bad while praising existing adoption and wanting more is highly hypocritical. We haven't even had a good chance to judge those possible future solutions and FUDsters are already calling the death of bitcoin if it's block size limit doesn't increase. Funnily enough, when not under a stress test, even the 1Mb limit seems big.