It may not be a big deal for a typical user (but 30-40% savings are also nice) but for exchanges that have a lot of large multi-signature P2SH transactions, the savings are more than 50%. I'm surprised the adoption is so slow because, say, Bitpay or Coinbase would save millions easily (last 24h the whole network paid miners about $2M-worth BTC in fees), especially since it will decongest the mempool so the savings would be more than just savings in the size of the transactions. But they apparently prefer to complain instead of doing their part.
Indeed, I'm just see it in my perspective but for big exchanges; they could save Million dollars fees within a month, a week, even every single day. There are few wallet developers which has been implemented P2SH-P2WPKH address as far as I know, such as Ledger wallet, bitcoin core, samourai wallet (on developing), and electrum 3.0. Ledger wallet is the first one I guess and electrum implemented segwit address after 2 months, not sure why this latest upgrade for segwit support is taking so long.