Get over it. DL is not rewarding anyone's flying or, for that matter, rewarding anyfor anything. SMs is a marketing tool with limited resources. You cannot UG everyone on the plane. If you give certain benefits to everyone they become less desirable. For example, if FO boarded with SP+, PMs and GMs would get crowded out of earlier boarding.
DL has made a decision how to allocate the limited resources. In many cases, DL has determined they can maximize the effectiveness of the marketing tool by limiting certain benefits to DM and/or PM and/or GM. It's obviously more cost effective and has a better impact on the bottom line if FOs are not included in certain benefits. Either accept what is being offered or move to a different airline.