Why did Voldemort Kill Ameila Susan Bones personally?

[Hagrid]

No: HPFGUIDX 168945

Aussie says:

Actually, Susan Bones (the student) lost her immediate family 17 years 
ago to Death Eaters. so it makes me wonder ...

... is LV killing off wizarding families for a reason?

Tom Riddle had little personal reasons to be resentful against 
families ... but other Dark forces may have.

Or are the Bones direct decendants of Helga Hufflepuff? Was that their 
importance?