Give us one reason why expanding the transaction throughput size (as has been done in the past) should not happen again, now?

Are you against bitcoin being used as a currency? Do you have a big position in Litecoin, Dash, or Monero and hope that Bitcoin will die so your preferred alt will flourish?

And segwit seems to open a lot of risk if we're going to separate the actual transaction from the thing that verifies the who, what, and when of the transaction.