Why is it a structural issue? Decimal places can be added if it's a question of having tradeable units, and over time avg losses will be predictable and not affect price much.
Because the prior division means that allocation becomes increasingly disalligned with actual values.
If "once accepted a pizza for bitcoin and forgot to convert it" quanities becomes worth a luxury car later no matter how much you sub divide it people are discouraged from actually using it as a currency and instead exchanging directly to avoid the future losses. Except that when everyone does that it becomes worthless because nobody is using it to exchange anything - the source of its value.
Predictable and known price fluctuations are not an issue for commerce. Their effects can be reliably factored into the transaction. Only wild and unpredictable changes in price create challenges.
