90% of the pilots job when cruising is getting ride reports to try to predict and avoid turbulence. He has the radar too. However it's impossible to predict so they go for a "better safe than sorry" policy. The FA will get calls from the flight deck. When you hear it over the PA then it probably means there isn't time to call because the turbulence is early or worse than expected. All this kinda depends on the pilot his level of sensitivity.

I've been on flights where half the liquid spilled out of my glass while sitting on the table from the turbulence and the service continued while others where they suspended service and it was smooth.
so I don't consider it lazy.

I do consider it lazy when they forget to turn off the seat belt sign.

Also I've was on a 2hr flight recently where they were expecting turbulence 45 min after take off to last through landing. The FAs did a water only service instead of a regular one. I found this to be lazy. It's certainly possible to finish in that amount of time.
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