After the Supreme Lord Narayana took everything that the King Bali had, Sri Narayana gave him a boon and with that boon Bali made the God as his gatekeeper.
Goddess Lakshmi had tied Rakhi to Bali, who had made the Lord of the three worlds (i.e. God) his gatekeeper. A feeling of gratitude is expressed towards the sister or the well – wisher. King Bali asked – “What do you want?” Lakshmiji said: “Set free your little watchman.” And thus Lord Narayana was released from the bond of being the gatekeeper.
Therefore in order to release Lord Narayana, who served as a gatekeeper being overpowered by the devotee’s love, even Lakshmiji makes use of Raksha-Bandhan festival.