Although I also wish smartphones had extra physical buttons. I still use a separate MP3 player mainly so I can skip tracks or change the volume without having to take it out of my pocket. (or mess around with poncy bluetooth headphones)
A lot of inexpensive in-ear headphones have inline remotes that allow for the control of basic playback functions. An app like Headset Button Controller allows you to customise the function of those buttons. An advantage of using a smartphone over an MP3 player is that you can use Google Now to control media playback using speech.
In-line remotes are nearly as bad, it cuts your choice of headphones down to about a quarter, and it's an extra thing on the cable to get snagged on things and break.
As for using google now, I'm not going to walk around Tesco shouting "next track"
It just annoys me because there's no good reason that my phone couldn't have an extra few buttons down the side, and I'm hoping that this line of minimalism is just a fad.
>>24312 I don't know how useful it'll be to you, but if you're rooted and have Xposed, then Gravitybox has a feature that lets you use the volume buttons to skip tracks by holding them down when the screen's off, so I just do that through my pocket.