Heirs Bond

My mom passed away two years ago. We have a joint time deposit account. Naka "and" lang kami so I was required by the bank to go to BIR to obtain CAR. After a year, dahil super bagal ng BIR, nakuha ko na yung CAR. So pagbalik ko sa bank atsaka ko pa lang nalaman na need pang ifile sa Register of Deeds yung documents. And aside from that they are requiring me to get an Heir's bond with two years validity. Just in case daw na may iba pang magclaim. I'm an only child, but since my father is alive, extrajudicial ang ginawa namin and nag waiver father ko. So I need someone to explain to me bakit kailangan pa nung heir bond? It's very expensive. Hindi naman kalakihan yung time deposit namin ng mom ko. Parang unfair po kasi, pera naman namin yun magiging bato pa. Hope someone can enlighten me. Thanks in advance!