"Some airlines claim these practices are necessary in order to stop ‘tariff abuse’ – when passengers buy return tickets that are cheaper than a single flight."
Tariff abuse, aka being financially savvy. A return shouldn't be cheaper than a single.

When I lived on Abu Dhabi - Etihad charged $100 per person if you did a name change within 21 days of departure on a group booking - BUT - not if the group was a direct booking. They insisted on knowing the group origins and within an hour or two their sales rep was knocking the group organisers door offering free upgrades to cancel and book direct.