Because most of my Splinterlands cards worth just/only a few cents. No one would rent those cards. Nowadays my total (personally owned) Splinterlands card collection is worth only around $240 USD. Currently a few valuable cards are delegated to me by various other kind and generous Splinterlands players, and this why PeakMonsters is showing a value of around $656 USD (without selecting any filter).
By putting a tick to "Yes" after the "Owned" filter, it shows a value around $240 USD. This is the total value of the 217 Splinterlands cards, which I currently own.
Yeah, the rents are non existent for the level one cards during season - but at the end of season, you might rent them :)