Many of my clients opt to have the sewer line on their house scoped as part to their inspections before buying a house. I have done it myself on the last two homes I have purchased. There are times when I think spending the roughly $200 to do a scope is a good idea and times when choosing to skip it is okay too.
The last two houses I purchased are older houses. One was built in 1955 and the other in 1926. I needed to know if the sewer line was original to the house and also its condition. Both houses also have numerous full sized trees growing near the sewer line. Tree roots can cause damage to sewer lines just as much as age can. I was fortunate that both lines are in great shape. And I know it for sure because it was checked. It helps me sleep a little easier at night.
I find that the $200ish I spend on each of those scopes was well worth the price. If they were in poor condition and needed replacing that could cost anywhere from $5,000 to $10,000. It's not a cheap repair. Or a fun one.
I always think that if you are buying an older house or a home with numerous mature trees near the sewer line it's a good idea to get that sewer line checked. I've also heard that if you have a new home being built where an older home once stood, you may want to check it too. There have been times where builders have tried to use the old line rather than run a new one.
A few years ago Salt Lake County partnered with Homeserve. It's an insurance company that will cover your water and sewer lines to your property for very minimal cost per month. I think it's something like $15 each month. It's a great service for homeowners in our older neighborhoods.
Those are my thoughts on sewer line scopes. I also know some reputable people who do scopes with out crazy upselling. Let me know if you ever need a recommendation.