GT-I9082 - Unable to enter download mode through ADB

I have a really old Samsung Galaxy Grand Duos from 5 years back. I want to boot into download mode using ADB. I am using the following command adb -s reboot download What this does is just reboot my phone and does not take me to recovery. I can boot into recovery though using adb reboot recovery I have tried the commands adb reboot bootloader also has no effect other than booting my phone. I can enter into recovery the manual way using volume down + power + home button, but why can't I enter it using ADB ? What am I doing wrong ? My phone is running Jellybean Samsung Stock ROM and does not have the fastboot/bootloader mode.