Well, the Iowa-class could do about 35 knots.
As
@Harada.Taro pointed out, that's not true. The hull length and form, and engine power, give a top speed of around 33 knots - comfortably faster than the 27-knot US fast battleships and the 21 to 24-knot speed of most WW1 designs. Where the story comes from is the
Iowas' habit of running away from their escorting destroyers. Since the DDs could make 35 knots, the BBs must be faster, right? In heavy weather or rough seas, yes - a big ship can continue to steam at top speed through waves that make a smaller ship slow down.
Of course you could design a battleship to make 36 knots, but by the time you could do it you wouldn't need or want to. Aircraft largely removed tactical speed from the equation - you can't run away from a plane - so strategic 'sustainable cruise speed' became more important. That's why today's carriers still steam at around 30 knots, just as carriers did in WW2. And high speed always comes at a price; you need a long hull and an enormous amount of horsepower generated by a big, heavy engineering plant. That takes up tonnage you'd otherwise spend on weapons and defenses. Most ships can reach 85-90% of their top speed on half to two-thirds of their power, it's the last 10-15% that's hard (and expensive) to get.