Miners have some influence. Segwit needs 95{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8} and BU 75{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8} of miners signaling.

That in turn means a small block of mining power (anything over 5{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8}) can block Segwit, and a slightly bigger block of mining power (anything over 25{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8}) can block BU.

If you are a miner, that's good for your bottom line. All things equal, having less capacity leads to higher fees. Miners like having higher fees. Their business is highly competitive, margins are small, so the extra fee income has a large influence on profits.

So the rational strategy for miners is to play both sides against each other. Make sure that there is no consensus either way, and keep the present fortunate state of affairs going for another couple of years.

And it is very easy to do right now. Miners can correctly explain that they would really love to help scale Bitcoin, but there just isn't the necessary level of consensus for either proposal. And then just lean back and enjoy the additional fee income.