Depending on the initial gravity... if t was north of 1.065, and you just pitchd a tube of yeast with no starter, I would expect a long lag phase. (Lag phase is when the yeast is multiplying, but not really making a lot of bubbles).
Liquid yeast tend to be sluggish out of the tube. Giving them a starter wakes them up and gets them ready to brew instead of sleep. (it also increases cell count). Putting a tube of yeast into a 1 pint starter will not increase cell count, but often takes a couple days off the lag phase in a 5 gallon batch. (my experience)
With more sugar in the beer, the yeast will multiply slower during the lag phase, and want to multiply more before starting active fermentation.
Those factors above, and I am willing to bet you may have your bucket in cooler temperatures... possibly 62F or so (how active a yeast is at lower temperatures is strain dependant so your mileage may vary)... and slow yeast's desire to kick into active fermentation. What I have observed is that with a yeast starter, the yeast will ferment just fine at lower temperatures. Out of the vial, with no starter, they need warmer temperatures to help them wake up. However, once they have been through a starter, even if it ferments completely out, I can ferment at 62 without issues. Out of the vial with no starter, it wiill take 4 or 5 days for it to finally get going.
So in the end, if you can do a starter.. do it! It is always a good idea.