As many of us know, YMMV rule applies widely here. These days, I relented and just carry one racquet diagonally inside my luggage, sandwiched between soft clothes. Never had any issue. Got tired of worrying and convincing multiple people (from ground during check-in, security at the gate, cabin crews during plane entrance, etc.).
I've been stopped when boarding and told it can be used as a "weapon". So, had to check it in on the spot - messed up all my grip, but lucky it's only the overgrip.
Having said that, I've dropped off a junior on her way to Florida for one of those high school+tennis program. She was carrying those 12-pack bag stuffed with clothes and racquets. She managed to pass the security gate, got scanned OK and was only stopped during boarding and had to check it in (for free, though).
Some airport's security guards in front of the area before you enter the queue to put your bags for scanning are very strict, they won't even let you pass for bags that doesn't fit the metal mold located at the entrance with the official allowed cabin bag size.
I've also been turned down by those security guards in front of the area and told to get a special tag from the check-in counter - implying that the airline 'approves' it for cabin.
So, I get tired of this and just put in my 30-inch luggage. These experiences above was for International travel.