Though all wine used to be sealed and closed with corks, many wine companies are making the switch to screw tops. This is not a reason of convenience but rather of necessity. Cork is made out the bark of the Cork Oak tree. When an infection began showing up in the wine corks it began to leak into the wine and make it contaminated. The resulting taste of the wine was tainted and companies began to switch over to screw caps to avoid tainting the wine. Though some wine makers still use corks for their wine, it is through very careful selection that they are not using contaminated cork. The easier and safer route for most is to choose the screw cap.
Though results have been mixed in taste tests done between corked and capped wines, there has not been so much in the way of researching the difference in taste. One of the differences that may be found between corked and capped wines is in the aging process. Cork is very breathable and for this reason it allows the wine to breathe well during the aging process. Screw caps do not have the same properties as cork and do not let the wine breathe as well. Some say that the difference is not an issue and others say that the only proper way to mature a red wine Sea Bright is with cork.
Besides this factor of aging the wine, there can be another issue that deals less with the taste of the wine but more with the formality of serving it. Many fine restaurants have a traditional ritual and method for beautifully uncorking and pouring their wine for diners. A wine with a screw off top can seem much less formal. As more wines become screw topped it may become more of normality for dining customers to see their wine being uncapped instead of uncorked.