Is it obligatory to abandon the Sunnah of raising the hands in prayer if the Imam does not do it, or to avoid annoying others, or to avoid the feeling of showing off?

Raising the hands during prayer is legislated in three instances: at the opening takbir by consensus, and when bowing and rising from it, which is a continuously transmitted Sunnah (definition), and when rising from the first tashahhud (definition). Consistently observing this Sunnah is recommended, and there is no sin in omitting it, but its reward is missed. What Satan whispers by way of ostentation must be resisted.