When used without "I" it's a synonym for "love ya"-- a casual sign-off, expressed with some light affection. Can be used by siblings, adult children, partners, significant others, dating couples, perhaps a spouse of several years but not between couples who are "in love" or parent and children in a bonding moment for whom "I love you" is more appropriate.
(In a phone message to spouse): I'll be a little late coming home tonight, love you.
(Adult child ending a visit to parents). Always good to see you both. Love you!
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