From my observations it seems that in general terms, pilots are loath to use anti-ice. It almost seems that one's not a real man (no offence intended to women pilots) if one uses anti-ice.
The number of times I've heard, "this isn't thick (cloud) I won't use the anti-ice", doesn't bear thinking. Also amusing to me are the folk toodling along in and out of cloud who turn the engine anti-ice on and off and on and off and ...
Each to their own with the second scenario but if one is in and out and in and out, why not just leave the engine anti-ice on until it's no longer needed?