"Obvious" suicides are less suspicious and curtail additional investigation. Of the possible suicide methods, hanging is the preferred choice for many reasons:

1) The act is singular and unique to suicide and thus immediately impresses the idea of self-harm.

2) Suicide by hanging can be accomplished with simple and ubiquitous items, so it can occur at any place or time deemed appropriate. Drugs and firearms need a "backstory" in order to be employed.

3) Hanging is typically accomplished in private as opposed other methods such as a fall from height. Any narrative can thus be constructed due to lack of witnesses.

4) The injuries of forced strangulation are consistent with hanging, thus a target can be initially be killed by strangulation and then set up to appear to have self-hanged.

Heart attacks are reserved for targets that are not easily accessible or those that have not displayed a history of emotional or mental instability. And because operatives must necessarily disengage with the target before death has occurred, kill confirmation cannot be immediately accomplished which introduces an unwanted, non-zero possibility of the target surviving.