When I go heavy/ lower rep sets, I prefer to not have a spotter. Reasons:
1.) Don't want them touching me or the bar, throwing off my balance.
2.) Its easier for me to drop the weight behind me (very easy to drop if you have proper technique throughout, i.e-chest up, spine in proper alignment, lower back arched naturally, weight on heels etc.) than to struggle to bring it up with a spotter
3.) Mentally you can't back off or quit like you could with a spotter. Without a spotter, you're like, "I gotta get this or I'm gonna look like an asshole".
Overall, for me there are more benefits of not having a spotter. It doesn't make it safer, in fact, it can be more dangerous, especially if mentally you are thinking your spotter is going to save you or you can have poor technique to try and get the weight since you have a spotter. I don't have to worry about another variable, I can drop it safely and I can be 100% committed to getting the lift or dropping it without having to worry about the guy behind me.