new service panel
Not knowing what you are planning to add or what services you currently have makes it difficult to assess however, if you are in the process of "upgrading and remodeling" you should do it right.
You currently have a service panel with less than normal capacity for a modern house. Depending on the size of the house and major appliances in use, you should have a 100a or much better 200a main. No matter what, you will need to have new service feeder connections to support a 200a service. This would also require a new meter box for 200a and a new panel for 200a. Changes will cost money both for parts and more so for labor. Although this is a DIY website, this work should be done by a licensed electrician after having the proper permits obtained.
The possible reason the previous owner didn't do this is because it can cost a significant amount of money depending on the amount of work involved.
Did you ever stop to think, then forget to start again?