I did some posting at-length last year regarding signal use, particularly as involving entrance-merging. Let me first state that it is a longstanding tenet of the interstate system that on-hwy traffic has obligation in the easement of entry of on-ramp traffic. Citation can be issued in this regard, such as for aggressively-impeding maneuvers, though I've never heard of one having been written. When I'm in the slow lane or other lane subject to entering (ramp) traffic, I keep a forward watch for entrants and modulate speed to accomodate their merging.
As to signaling, if you're accelerating on a merge ramp, your intention should be crystal-clear to on-hwy drivers (or to self-driving vehicles, etc.)- you're coming onto the lane the ramp merges to (duh, there's nowhere otherwise to go). The utility in putting on a turn signal is nil. There is no need to advance-communicate the obvious, that you are merging onto the hwy. I might make exception for a case where I would be looking to further change lanes immediately upon entry, to advise traffic of single or multiple lane change that may not at all be so obvious.
The purpose of signaling should be to communicate intent to others with advance need to know, either of making a turn or a lane change. I'm libertarian enough to believe there should be no requirement to put on signal simply as a matter of rote for every turn or lane change regardless of whether there's any other traffic to be signaled to. A citation for lack of signal should necessarily be accompanied by a statement as to another's advance need to know having gone unmet.
Finally, I would have to agree that seeing a car up ahead on a ramp with its blinker on indicates a possibly inexperienced and/or timid driver. I take particular note of its speed, as these may be coming on quite slowly rather than more-properly accelerating to near the hwy prevailing speed (and may be slowing down others behind it as well, into a big, slow clump), and I may need to alertly either accelerate to clear it, to change lanes or to (ugh) slow down.
But it IS my obligation to address its safe entry.