In the novel I was recently reading, one of the dialogues went something like this:
"Don't put lighter fluid in the wood stove," she said.
"You think it will explode?" he asked.
"Maybe. It's definitely dangerous."
"I suppose I'm playing with fire, ha, ha."
"It probably depends on how hot the stove is."
"And how volatile lighter fluid is."
"Are there different kinds of lighter fluid?"
"Good question. Either way, there must be safer fire starters for stoves."
"What about those wax logs?"
"I've never tried that. Do you have to start with kindling? Or can you just light them with a match?"
"I don't know, but I've heard that if you break them up when they're burning, they become an inferno."
At about this point, I'd gone back two different times to try to figure out who was speaking. There are few things more frustrating.
Yes, the dialogue could have been constructed to make the identity of the speaker more obvious. But this confusion happens to all of us readers. So why do writers do this? If you asked the writer, he would probably say it is obvious who the speaker is, and that those pesky 'he said, she said' dialogue tags are obnoxious. Sure, it's obvious to writer. But the rest of us are in the dark.
In an ideal world, the different speakers would have speaking styles so distinct that the reader could tell who is speaking just by the words. The problem is that the author knows who's speaking, so the author can't adequately judge how clear it will be to the reader. In addition, maybe the reader is fatigued, reading in bed, not paying careful attention to what they're reading. (I know, shocking to consider that, huh?!)
The bottom line is that when in doubt, writers should insert a 'he said' or 'she said' every now and then to help make it clear. (Or 'Joe said' or 'Susan said')
There are variations on the theme using action.
Susan was drinking a beer when she saw Joe open the door of the wood stove. "Don't put lighter fluid in the stove."
"You think it will explode?" Joe looked at the charcoal lighter bottle.
The writer can often utilize this, but it can become tedious.
He said or she said is largely invisible. And no matter how much you don't like it, it is better than making your reader get out a pencil and making her own dialogue tags in the margins.
P.S. Whatever you do, don't put in dramatic dialogue tags like he retorted, she barked angrily, he yelled at the top of his lungs. Those are over-the-top cliches and call unnecessary attention to themselves, distracting readers away from the very dialogue you are trying to perfect.