Tiberius is an influential man with his work for the Ministry of Magic. As an Unspeakable he doesn't have to answer to the Ministry, a position that makes influential people want to become his friend. He gets invited to parties, quidditch matches and basically gets anything he wants. It's a life he got used to. A life he isn't ready to give up yet despite the threat coming closer.

His wife publicity chose the side of The Order, but Tiberius thinks he can keep her safe as long as he doesn’t pick a side yet. Does he agree with her? For sure, but their safety and perhaps a little selfish, his work, was more important than picking a side at the moment.

It's something the man struggles with because of the history of his wife and him; where she chose to leave the sacred 28 to be with him. She literally gave up everything for him. The same people that disowned her are now Death Eaters so, he knows they don't approve of him, and he knows they don’t like his wife, but to choose a side and perhaps their family becoming a target? He was conflicted. 

Tiberius always jokes with his co-workers that a happy wife is a happy life, and he agrees. The man does everything to keep her happy. He perhaps has a weird way of showing it since he loves to buy her things. You can say he’s a little materialistic and that’s why he often shows his love by buying her things. It’s not that he feels like he HAS too, but he wants too. He loves to spoil his wife with dinners, jewelry and holidays together. 

To be fair, he wouldn’t be as great as he is in his job without Cass. When Cass got disowned, his family didn’t have much, and he worked his ass off to make sure his wife got everything she wanted. After all, she picked him, and he will always pick her.